Ec Lab Manual (08.407) 1l1v
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Electronic Circuit Lab Manual Expt. No. 1
SERIES VOLTAGE REGULATOR Objective: Aim of the experiment is to understand the operation of simple series voltage regulator Equipments and Components Required: 1. Digital Multimeters (DMM). 2. DC power supply. 3. Project Breadboard. 4. Resistors. 5. BC107 BJT 6. Zener diode. 7. Connection Wires. Circuit Diagram:
Design: Given that Vo = 15V, ILmin = 1mA, ILmax = 100mA, Vin min = 16V, Vin max = 30V, IZ max = 100mA and β = 100 Optimum value of Optimum value of
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and and
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Electronic Circuit Lab Manual Procedure: 1. Test all components 2. Connect the circuit diagram 3. Connect the variable dc power supply as input and turn on. 4. Vary the input voltage from 0 to 30V and note down the corresponding output voltage
using voltmeter for line regulation 5. Turn off the power supply 6. Replace RL with 100k pot in series with RLmin
7. Turn on power supply and set it to 20V 8. Vary the pot from higher position to lower position, note down the output voltage using voltmeter and load current using ammeter for load regulation Pre-Lab Assignments: 1. If 15Vpp sinusoidal input voltage is applied to the circuit shown above, sketch the output waveform. 2.
If the input Vin = 10V and R1 = 10kΩ , calculate I1 and IZ, where VZ = 5.2V and β =
50. 3.
If R1 reduces what is the improvement of the circuit?
4.
Derive the expression for Vo of the circuit shown in fig.1
5.
Find optimum value of R1.
6.
How does changing RL affect Vo?
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Electronic Circuit Lab Manual Model Characteristics: Line Regulation:
Load Regulation
OBSERVATIONS Design parameters and components used: Vo = 15V, ILmin = 1mA, ILmax = 100mA, Vin min = 16V , Vin max = 30V, IZ max = 100mA and β = 100 (For maximum current) 10Ω to 1.5k Ω
(For minimum current)
Tabular Column Line regulation RLmax=15kΩ, R1max=1.5kΩ Vin(V) 0 1 2 3 4 5 6 7 8 9 10 11 12 14 15 16 17 18 20 30
Vo(V) 0 1.3 1.2 2.2 3.2 4.1 5.1 5.9 6.9 7.9 8.8 9.8 10.5 12.2 13.2 14 14.4 14.6 14.6 14.6
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Electronic Circuit Lab Manual Load regulation Vin = 30V, RLmin = 150Ω IL(mA) Vo(V) 0 15 1 14.8 2 14.7 4 14.7 7 14.7 8 14.7 9 14.7 10 14.7 50 14.7
Viva Questions:: 1. Define regulation. List out different types of regulators. 2. Define line and load regulation. 3. What is percentage of voltage regulation? 4. Compare different types of regulators. 5. Draw the basic block diagram of series voltage regulator.
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Electronic Circuit Lab Manual Expt. No. 2
POWER AMPLIFIERS Objective: The aim of the experiment is to study the operation and efficiency of Class B and Class AB power amplifiers Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100, SK100 BJTs 1N4007 Diodes Connection Wires. Oscilloscope Probes.
Circuit diagram: Class B Power Amplifier:
Fig. 1 Department of ECE, VKCET
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Electronic Circuit Lab Manual Theory: Class B circuit provides an output signal varying over one-half the input signal cycle, or for 180° of signal. The dc bias point for class B is therefore at 0 V, with the output then varying from this bias point for a half cycle. Obviously, the output is not a faithful reproduction of the input if only one half-cycle is present. Two class B operations—one to provide output on the positive output half-cycle and another to provide operation on the negative-output half-cycle are necessary. The combined half-cycles then provide an output for a full 360° of operation. This type of connection is referred to as push-pull operation. An amplifier may be biased at a dc level above the zero base current level of class B and above one-half the supply voltage level of class A; this bias condition is class AB. Class AB operation still requires a push-pull connection to achieve a full output cycle, but the dc bias level is usually closer to the zero base current level for better power efficiency. For class AB operation, the output signal swing occurs between 180° and 360° and is neither class A nor class B operation. Following figure shows a diagram for push-pull operation.
An ac input signal is applied to the push-pull circuit, with each half operating on alternate half-cycles, the load then receiving a signal for the full ac cycle. The power transistors used in the push-pull circuit are capable of delivering the desired power to the load, and the class B operation of these transistors provides greater efficiency than was possible using a single transistor in class A operation. DC Analysis: The dc power supplied to the load by an amplifier is given by
AC Analysis: Output power is given by The efficiency of Class B amplifier can be calculated by Maximum η of Class B operation is given by 78.5% The power dissipated by the individual output transistor is given by
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Electronic Circuit Lab Manual Design: Given that The transistors are as emitter follower.
Output power,
Input power, Efficiency, Power dissipation by each transistor, For R1: Under dc conditions,
and To keep transistor at cut-off region under dc biased condition I1 should be low.
And
.
For R2: Class B operation R2 should be negligible. Use the equation Department of ECE, VKCET
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Electronic Circuit Lab Manual
Choose For Class AB operation
or replace the resistors with diodes
Choose Note: Try to observe the output for different R2 For coupling capacitors:
Choose
and
Procedure: Steps: 1. Check the components 2. Connect the circuit (use R1 for class B operation) 3. Turn on the power supply and apply input signal vin (1Vpp) from function generator
4. Connect CRO probes channel 1 to input and channel 2 to output 5. Observe the input and output wave forms and measure I dc by setting vin =0V and Io
vin=1Vpp, also measure corresponding Vo 6. Turn off the power supply 7. Replace R1 for Class AB operation
8. Turn on power supply 9. Observe the input and output wave forms and measure I dc by setting vin =0V and Io
vin=1Vpp, also measure corresponding Vo Department of ECE, VKCET
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. What is the ideal DC value of the output signal of Class B and Class AB amplifier if there is no input? Compare this with Class A amplifier. 2. Plot one of the collector current (I ) vs. time, is it full-wave of half-wave? 3. Derive expressions for of Class B power amplifier. 4. List out the advantages and disadvantages of Class A, Class B, Class AB power, Class C and Class D amplifiers. C
5. Design the circuits shown in fig.1 for
, β =100,
and draw the output wave form for sinusoidal input. Model Waveforms: Class B power amplifier:
Class AB power amplifier:
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Electronic Circuit Lab Manual Simulated Results: Efficiency: Class B Power Amplifier: R1=24kΩ (If it is very high, η can be increased to ideal value), R2=100Ω , RMS current delivered from source during the operation
Class AB Power Amplifier (R2=10k ) : , RMS current delivered from source during the operation
OBSERVATIONS Design parameters and components used:
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Electronic Circuit Lab Manual Input and Output waveforms: Class B
Class AB
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Electronic Circuit Lab Manual
Efficiency Class B
(?) Not satisfied. This is due to the lack of true RMS meter Class AB
(?) Not satisfied. This is due to the lack of true rms meter Viva Questions: 1. Differentiate Voltage Amplifiers and Power Amplifiers. 2. Classify Power amplifiers. Department of ECE, VKCET
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Electronic Circuit Lab Manual 3. Define efficiency of Power Amplifiers. 4. Suggest a way (with a diagram) how you might be able to improve the biasing to eliminate the crossover distortion. 5. How you might reduce distortion by using a negative ? 6. What is the practical application of power amplifiers?
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Electronic Circuit Lab Manual Expt. No. 3
DIFFERENTIAL AMPLIFIER USING BJT Objective: The aim of the experiment is to study the operation of differential amplifiers using BJT and obtain CMRR and input resistance. Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors 7. Diodes 1N4007 8. BC 107 or SL100 BJTs 9. Connection Wires. 10. Oscilloscope Probes. Circuit diagram: a) Differential Amplifier using BJT: i)
Differential Mode, Balanced Output (for differential gain)
Fig. 1
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Electronic Circuit Lab Manual ii)
Common mode, balanced output (for common mode gain)
Fig. 2 Different Modes: a) Dual input balanced output The circuit is same as shown in Fig. 1 b) Dual input unbalanced output The input is same as above, but output is taking across any of the transistor’s collector and ground. c) Single input balanced output. One of the inputs set to ground and output is same as first mode. d) Single input unbalanced output. One of the inputs set to ground and output is same as second mode.
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Electronic Circuit Lab Manual Power Supply Arrangement for Dual Voltage Source:
Fig. 3 Note: For unbalanced output use coupling capacitor at the output Theory: The differential amplifier, or differential pair, is an essential building block in all integrated amplifiers. In general, the input stage of any anategrated circuit with more than one input consists of a differential pair or differential amplifier. The basic differential pair circuit consists of two-matched transistors Q1and Q2 , whose emitters are ed together and biased by the constant current source circuit. Q1, D1, D2, R2 and RE acts as current source, which introduce constant current IEE to the differential amplifier with high ac source resistance, since ac equivalent of this dc current source is ideally open circuit. The important characteristics of the differential amplifier are: the common-mode rejection ratio CMRR, the input differential resistance R id, and the differential-mode gain Ad. Differential gain: , where Vid is differential input voltage,
and Vod is differential
output. For a perfectly matched pair transistor differential gain should be infinite.
CMRR: Common Mode Rejection Ratio, and it is
, where Vcm is common mode input voltage,
, where Ac is common mode gain and Voc is common
mode output. For perfectly matched pair transistor common mode gain should be zero, and then CMRR should be infinite. Differential input resistance: The resistance between the differential input and ideally it should be infinite.
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Electronic Circuit Lab Manual DC Analysis:
For constant current source circuit:
AC Analysis: Balanced output Mode: Differential gain Common mode gain CMRR Differential mode input resistance Output resistance Unbalanced output Mode: Differential gain Common mode gain CMRR Differential mode input resistance Output resistance Resistance of current source circuit:
Design: Given that From data sheet of BC 107,
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,
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Electronic Circuit Lab Manual
From the above design:
,
Procedure: Steps 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply and apply differential input signals v 1 and v2 using
function generator 4. Connect CRO probe of channel 1 to one input and channel 2 to unbalanced
output vo1 via a coupling capacitor, observe the differential input and output for differential gain 5. Repeat the above step for other vo2
6. Connect channel 2 probe across the collector of transistors without coupling capacitors 7. Observe the balanced output voltage for differential gain 8. Apply same signal to the two inputs as common mode input 9. Repeat step 6 and observe input and output for common mode gain Department of ECE, VKCET
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Define CMRR. 2. Draw the basic circuit of differential amplifier using BJT. Give the significance of
RC and REE 3. Design differential amplifier with current source circuit using BJT using the following specifications 4.
5. Give the use of current mirror circuit in differential amplifier. 6. Give the advantages of MOSFET differential amplifier. 7. Design differential amplifier with current source circuit using MOSFET using the following specifications
8. Draw the differential amplifier circuit using BJT with active load. Model Waveforms: Differential Input and Balanced Output
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Electronic Circuit Lab Manual Differential Input and Unbalanced Output
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Electronic Circuit Lab Manual Common Mode Input Unbalanced Output
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Electronic Circuit Lab Manual Simulated Results: Differential Gain: For balanced output:
For unbalanced output:
Common Mode Gain:
OBSERVATIONS Design parameters and components used:
From data sheet of BC 107,
,
Differential Mode: Input and output wave forms:
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Electronic Circuit Lab Manual i)
Balanced output:
ii)
Unbalanced output:
Common Mode: Input and output wave forms:
i)
Balanced output:
Viva Questions: 1) Define differential amplifier and give its application 2) Draw a current mirror circuit. Differentiate it with constant current source. 3) In a differential amplifier |VCC| ≠ |VEE|, list out the problems
4) Differentiate different configurations of differential amplifiers. Which one is commonly used? 5) Give the main advantage of constant current bias over emitter bias. Department of ECE, VKCET
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Electronic Circuit Lab Manual Expt. No. 4
CASCADE AMPLIFIER Objective: The aim of the experiment is to study the operation of cascade amplifier and obtain the frequency response and bandwidth Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100 BJTs Connection Wires. Oscilloscope Probes.
Circuit diagram:
Fig. 1
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Electronic Circuit Lab Manual Theory: A single stage of amplification is not enough for a particular application. The overall gain can be increased by using more than one stage, so when two amplifiers are connected in such a way that the output signal of the first serves as the input signal to the second, the amplifiers are said to be connected in cascade. The most common cascade arrangement is the common-emitter RC coupled cascade amplifier. Common-emitter amplifier exhibit high voltage, high current, and high power gains, so they are very familiar than other configurations. Multistage amplifiers can be used either to increase the overall small signal voltage gain, or to provide an overall voltage gain greater than 1, with a very low output resistance. Figure 1 shows an RC-coupled cascaded amplifier. Capacitors C1 and C2 couple the signal into Q1 and Q2, respectively. C3 is used for coupling the signal from Q 2 to its load. If the operation of coupled amplifiers is considered, a complicating factor appears. The addition of a second stage may alter the characteristics of the first stage and thus affect the level of signal fed to the second stage. To compute the overall gain of the amplifier, it is easier to calculate unloaded voltage gain for each stage, then including the loading effect by computing voltage dividers for the output resistance and input resistance of the following stage. This idea is illustrated in figure 2. Each transistor is drawn as an amplifier consisting of an input resistance R in , an output resistance, Rout along with its unloaded gain, AV(NL).
Fig. 2
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Electronic Circuit Lab Manual Then, the overall loaded gain A V , of this amplifier can be found by:
For the RC Coupled (CE - CE) multistage amplifier with CE:
and Note that if a load resistor was added across the output, an additional voltage divider consisting of the output resistance of the second stage and the added load resistor is used to compute the new gain. If
and
DC Analysis: For 1st stage amplifier:
Where,
and
Stability factor For 2nd stage amplifier the analysis is same.
AC Analysis: For 1st stage amplifier: Voltage gain,
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Electronic Circuit Lab Manual Input resistance, Output resistance, For 2 stage amplifier: Voltage gain, nd
Input resistance, Output resistance, Design: Given that
For 2nd stage amplifier:
For
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Electronic Circuit Lab Manual From the above design
, where
For 1st stage amplifier:
For
From the above design
, where
For capacitors:
Where
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Electronic Circuit Lab Manual
Procedure: Steps 1. Check the components 2. Connect the circuit diagram for second stage amplifier 3. Turn on the power supply, apply input signal of voltage 10mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz)
6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note
down the corresponding output voltage for plotting frequency response 8. Turn off the power supply and construct first stage of amplifier and coupled its output to second stage. 9. Turn on the power supply, apply input signal of voltage 1mVpp (low voltage) to the input using function generator 10. Repeat the steps 4 to 7 Pre-lab Assignments: 1. Find the Q-point of each stage of the circuit shown in fig.1, where R 1 = R3 =
20kΩ, R2 = R4 = 10kΩ, RE1=RE2= 1kΩ, RC1=4kΩ, RC2=1kΩ VCC = 15V, VCE1= VCE2=0.2V, VBE1= VBE2=0.6V 2. Re-design the components of the circuit shown in fig. 1 for fL=1kHz
3. Define Power gain, Voltage gain and Current gain. How it represent in dB? Department of ECE, VKCET
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Electronic Circuit Lab Manual 4. What is transition frequency of transistor? Give the typical value for the given
transistor. 5. Simulate the circuit given in experiment using SPICE. Compare designed and simulated dc biasing conditions, show input and its corresponding output wave forms, plot frequency response and compare it with designed values. Model Waveforms: Input Wave form:
Output Waveforms (1st stage and 2nd stage):
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Electronic Circuit Lab Manual Tabular Column: For Single Stage Amplifier:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Av in dB
For Two Stage Amplifier:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Av in dB
Simulated Results:
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Electronic Circuit Lab Manual First Stage Mid band gain = 21.9dB Lower cutoff frequency fL = 192Hz Upper cutoff frequency fH = 4.3MHz Bandwidth = 4.3MHz Multi stage Mid band gain = 46.3dB Lower cutoff frequency fL = 257Hz Upper cutoff frequency fH = 4.15MHz Bandwidth = 4.15MHz OBSERVATIONS Design parameters and components used:
Input and output waveforms: Single stage:
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Electronic Circuit Lab Manual Two stage:
Tabular column: Single stage amplifier
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Two Stage Amplifier:
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Viva Questions: 7. What are the requirements of biasing and coupling circuits in BJT amplifiers? 8. What is the use of CE in RC coupled amplifier and give its influence in frequency response? 9. Give the advantages and disadvantages of cascade amplifier. 10. What is half-power frequency? 11. In amplifiers, why mid frequency gain is independent to frequency? 12. What is bode-plot? 13. What is the method to increase the output voltage swing of an amplifier? 14. How load resistances influence the gain of BJT amplifiers? 15. What is SPICE?
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Electronic Circuit Lab Manual Expt. No. 5
CASCODE AMPLIFIER Objectives: a) To study the operation of cascode amplifier using BJT and obtain the frequency response and bandwidth. b) To simulate cascode amplifier circuit using SPICE. Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. BEL100N BJTs Connection Wires. Oscilloscope Probes.
Circuit diagram: a) Cascode amplifier using BJT
Fig. 1
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Electronic Circuit Lab Manual Theory: The bandwidth of CE amplifier is limited due to the Miller capacitance effect at high frequency operation. This can be overcome by using adding a second stage CB amplifier (direct coupling with CE stage). This arrangement is called cascode amplifier. This amplifier has high bandwidth due to the reduction in Miller capacitance effect. The gain of the amplifier is high due the overall gain of CE and CB stage. The circuit has an input characteristics of CE amplifier and output characteristics of CB amplifier. In fig.1 R1, R2, and R3 form biasing network for Q1 and Q2; C1 and C3 for coupling ac signals; C2 and CE for bying resistors R2 and RE, respectively at ac signals. Transistors Q1 and Q2 should be identical DC Analysis:
AC Analysis: Voltage gain, Current gain,
, where
Input resistance, Output resistance, Design: Given that Find typical value of β from the data sheet of BEL100N.
(To get maximum output swing keeps Q1 collector voltage low) (To get maximum output swing keeps Q2 collector voltage 50% of VCC) Department of ECE, VKCET
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Electronic Circuit Lab Manual
Procedure: Steps 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply, apply input signal of voltage 10mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz) 6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response Department of ECE, VKCET
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
Where
. Find Voltage gain, Current gain Input impedance and Output impedance of the circuit 2. Simulate the above circuit (use
using SPICE and submit: a) Circuit diagram with dc bias voltages, b) Input and output wave forms and c) Frequency response curve
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Electronic Circuit Lab Manual Model Waveforms: Input Wave form:
Output Waveform:
Tabular Column:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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log10f
Av in dB
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Electronic Circuit Lab Manual Simulated Results:
Mid band gain =37.2dB Lower cutoff frequency fL = 752 kHz Higher cutoff frequency fH = 24MHz Bandwidth = 25.8MHz OBSERVATIONS Design parameters and components used: Given that
Input and output wave forms
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Electronic Circuit Lab Manual Tabular Column:
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Viva Questions: 9. Define miller effect. 10. Say the advantages and disadvantages of CE, CC and CB configuration of BJT. 11. How the bandwidth improved in cascode amplifier? 12. Which multistage amplifier has maximum bandwidth? 13. Give the expression for current gain of cascode amplifier using BJT. 14. What are the applications of cascode amplifier? 15. In an amplifier which factors limits gain at low and high frequencies?
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Electronic Circuit Lab Manual Expt. No. 6
FEED BACK AMPLIFIERS Objectives: a) To study the operation of voltage series negative amplifier and obtain the frequency response and bandwidth b) To study the operation of current series negative amplifier and obtain the frequency response and bandwidth Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors. 7. SL100 BJTs / BEL100N/BC107 8. Connection Wires. 9. Oscilloscope Probes. Circuit diagram: a) Voltage series negative amplifier i)
Without feed back
Fig.1 Department of ECE, VKCET
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Electronic Circuit Lab Manual ii)
With
Fig. 2 b) Current series negative amplifier: i)
Without
Fig. 3
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Electronic Circuit Lab Manual ii)
With
Fig. 4 Theory: A amplifier is one in which the output signal is sampled and fed back to the input to form an error signal that drives the amplifier. The basic block diagram of amplifier is shown below.
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Electronic Circuit Lab Manual The input signal, Vs, is applied to a mixer network, where it is combined with a signal, Vf. The difference of these signals, Vi, is then the input voltage to the amplifier. A portion of the amplifier output, Vo, is connected to the network of gain k, which provides a reduced portion of the output as signal to the input mixer network. If the signal is of opposite polarity to the input signal, negative results otherwise positive . The advantages of negative are: 1. Higher input impedance. 2. Better stabilized voltage gain. 3. Improved frequency response. 4. Lower output impedance. 5. Reduced noise. 6. More linear operation. Four basic types of connections along with the properties are given below:
Series-Shunt (Voltage-Series) Shunt-Shunt (Voltage-Shunt) Series-Series (Current-Series) Shunt-Series (Current-Shunt) In the list above, voltage refers to connecting the output voltage as input to the network; current refers to tapping off some output current through the network. Series refers to connecting the signal in series with the input signal voltage; shunt refers to connecting the signal in shunt (parallel) with an input current source. Series connections tend to increase the input resistance, while shunt connections tend to decrease the input resistance. Voltage tends to decrease the output impedance, while current tends to increase the output impedance. The gain and factor of four configurations are given below:
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Electronic Circuit Lab Manual a) Voltage Series Figure 2 show two-stage RC coupled amplifier cascaded with voltage series . The cascade amplifier gain with input loop and it opposes
, gain
. The part of output voltage (
and gain is to the
and results voltage series negative . If
,
the amplifier gain is b) Current Series Figure 4 show single stage RC coupled amplifier with current series . The gain of the amplifier without (with CE) . The element is RE . The gain of the amplifier with current
is fed back to the input (
opposes the input voltage
. Here the output ) is fed back to the input and it
. The gain of the circuit is
Design: a) Voltage series amplifier: Given that
For 2nd stage amplifier:
For
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Electronic Circuit Lab Manual
From the above design
, where
For 1st stage amplifier:
For
From the above design
, where
For capacitors:
Where
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Electronic Circuit Lab Manual
For obtaining higher cutoff frequency: where
and
(considering first stage)
From datasheet
For network:
Let
From the above design theoretical values of: Voltage gain with
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Electronic Circuit Lab Manual Lower cutoff frequency without Lower cutoff frequency with b) Current series amplifier: Given that
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Electronic Circuit Lab Manual
From the above design theoretical values of: Voltage gain with , Conductance Gain without Conductance Gain with Lower cutoff frequency without Lower cutoff frequency with Procedure: Steps (Voltage series ) 2. Check the components 3. Connect the circuit diagram without 4. Turn on the power supply, apply input signal of voltage 2mVpp (low voltage) to the
input using function generator 5. Connect CRO channel 1 probe to input and channel 2 to output. 6. Adjust the input signal frequency to mid band (10kHz) 7. Observe the input and output signal and measure the mid band gain 8. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response 9. Turn off the power supply. 10. Connect the circuit 11. Turn on the power supply, apply input signal of voltage 10mVpp to the input using
function generator 12. Connect CRO channel 1 probe to input and channel 2 to output. 13. Adjust the input signal frequency to mid band (10kHz) Department of ECE, VKCET
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Electronic Circuit Lab Manual 14. Observe the input and output signal and measure the mid band gain 15. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response Steps (Current series ) 1. Check the components 2. Connect the circuit diagram without 3. Turn on the power supply, apply input signal of voltage 2mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz) 6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response 8. Turn off the power supply. 9. Connect the circuit (Remove CE )
10. Turn on the power supply, apply input signal of voltage 10mVpp to the input using function generator 11. Connect CRO channel 1 probe to input and channel 2 to output. 12. Adjust the input signal frequency to mid band (10kHz) 13. Observe the input and output signal and measure the mid band gain 14. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
If
Find a) factor b) Voltage gain without and with c) Input impedance without and with d) Output impedance without and with 2. Simulate the circuits shown in fig.1 to fig.2. Submit the following: a) Input and output waveforms b) Frequency response.
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Electronic Circuit Lab Manual
3. Consider the following circuit.
Find bandwidth of the circuit where
Model Waveforms and Frequency Response: Voltage Series Amplifier without : Input Wave form and Output Waveforms:
vin=2mVpp vo = 356mVpp Department of ECE, VKCET
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Electronic Circuit Lab Manual Frequency response:
Voltage Series Amplifier with : Input Wave form and Output Waveforms:
vin=20mVpp, vo = 28.8mVpp Frequency response:
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Electronic Circuit Lab Manual Current Series Amplifier without : Input Wave form and Output Waveforms:
vin=20mVpp vo = 5Vpp Frequency response:
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Electronic Circuit Lab Manual Current Series Amplifier with : Input Wave form and Output Waveforms:
vin=10mVpp, vo 25mVpp Frequency response:
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Electronic Circuit Lab Manual Tabular Column: Voltage Series Amplifier without :
Input Signal Frequency, f (Hz)
Output Voltage Voltage, Gain, Av vo (vpp)
Av in dB
Voltage Series Amplifier with :
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Current Series Amplifier without :
Input Output Voltage Av in dB Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Voltage Series Amplifier with :
Input Output Voltage Signal Voltage, Gain, Av Frequency, vo (vpp) f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Simulated Results: a) Voltage Series without :
Mid band gain = 45dB Lower cutoff frequency fL = 1.21kHz Upper cutoff frequency fH =4.33MHz Bandwidth = 4.32MHz b) Voltage Series with :
Mid band gain = 32.4dB Lower cutoff frequency fL = 931Hz Upper cutoff frequency fH = 5.48MHz Bandwidth = 5.479MHz c) Current Series without :
Mid band gain = 46.3dB Lower cutoff frequency fL = 1.12kHz Upper cutoff frequency fH =2.46MHz Bandwidth = 2.458MHz d) Currente Series with :
Mid band gain = 6.25dB Lower cutoff frequency fL = 816Hz Upper cutoff frequency fH = 12.2MHz Bandwidth = 12.2MHz OBSERVATIONS Voltage Series : Design parameters and components used:
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Electronic Circuit Lab Manual
For network:
Input and output wave forms: i)
Without
ii)
With
Tabular Column: i)
Without
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
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Voltage Gain, Av
Av in dB
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Electronic Circuit Lab Manual ii)
With
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Current Series : Design parameters and components used:
Input and output wave forms: i)
Without
ii) With
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Electronic Circuit Lab Manual Tabular Column: i)
Without
Input Signal Frequency, f (Hz)
ii)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Voltage Gain, Av
Av in dB
With
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
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Electronic Circuit Lab Manual Viva Questions: 1. What are the types of mixing and sampling used in voltage series and current series ? 2. What is the effect of on the input and output resistances in various ? 3. What is the effect of negative ? 4. Show that the gain with is independent of amplifier parameters. 5. What is meant by gain de-sensitivity?
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Electronic Circuit Lab Manual Expt. No. 7
MULTIVIBRATORS Objectives:
a) To study the operation of astable, monostable and bistable multivibrators b) To simulate multivibrator circuits using PSPICE
Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100 BJTs / BEL100N/BC107 Connection Wires. Oscilloscope Probes.
Circuit diagram: a) Astable multivibrator:
Fig.1
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Electronic Circuit Lab Manual b) Monostable multivibrator:
Fig. 2 c) Bistable multivibrator
Fig. 3
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Electronic Circuit Lab Manual Theory: Multivibrators are switching circuits and switches between a "HIGH" state and a "LOW" state producing a continuous output. They can be used as oscillators, timers and flip-flops. The circuit can be characterized by two amplifying devices (transistors) cross-coupled by resistors or capacitors. There are basically three types of multivibrator circuits: Astable - A free-running multivibrator that has NO stable states but switches continuously between two states this action produces a train of square wave pulses at a fixed frequency. Monostable - A one-shot multivibrator that has only ONE stable state and is triggered externally with it returning back to its first stable state. Bistable - A flip-flop that has TWO stable states that produces a single pulse either positive or negative in value. Fig. 1 shows the circuit diagram of astable multivibrator. The circuit has two stable states that change alternatively with maximum transition rate because of the "accelerating" positive . It is implemented by the coupling capacitors C1 and C2 that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. In each state, one transistor is switched on and the other is switched off. Accordingly, one fully charged capacitor discharges (reverse charges) slowly thus converting the time into an exponentially changing voltage. At the same time, the other empty capacitor quickly charges thus restoring its charge (the first capacitor acts as a time-setting capacitor and the second prepares to play this role in the next state). The circuit operation is based on the fact that the forward-biased base-emitter junction of the switched-on bipolar transistor can provide a path for the capacitor restoration. The switching periods of each transistor are time
period
and
frequency
of
square
. Thus output
at
collector
of
transistor
is
where Figure 2 shows the circuit diagram of monostable multivibrator with trigger circuit. In this one resistive-capacitive network is replaced by a resistive network (just a resistor). The Department of ECE, VKCET
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Electronic Circuit Lab Manual circuit can be thought as a half astable multivibrator. When triggered by an input pulse, a monostable multivibrator will switch to its unstable position for a period of time, and then return to its stable state. The time period monostable multivibrator remains in unstable state is given by (at collector output of Q2 or
at collector of Q1). If repeated
application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable. If further trigger pulses do not affect the period, the circuit is a non-retriggerable multivibrator. In the bistable multivibrator (shown in Figure 3), both the resistive-capacitive network are replaced by resistive networks (just resistors or direct coupling).This latch circuit is similar to an astable multivibrator, except that there is no charge or discharge time, due to the absence of capacitors. Hence, when the circuit is switched on, if Q1 is on, its collector is at 0 V. As a result, Q2 gets switched off. This results in more than half +V volts being applied to R4 causing current into the base of Q1, thus keeping it on. Thus, the circuit remains stable in a single state continuously. Similarly, Q2 remains on continuously, if it happens to get switched on first. Switching of state can be done via Set (S) and Reset (R) terminals connected to the bases. For example, if Q1 is on and Set is grounded momentarily, this switches Q 1 off, and makes Q2 on. Thus, Set is used to "set" Q2 on, and Reset is used to "reset" it to off state. Design: 1. Astable multivibrator: i) Symmetry wave: Given that For symmetrical wave We have
Choose Then Department of ECE, VKCET
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Electronic Circuit Lab Manual Base current Collector current Condition for oscillation
and
For that
ii) Asymmetry wave: Given that We have Choose
Then
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Electronic Circuit Lab Manual 2. Monostable multivibrator: Given that trigger signal Ti=2ms
and time period of
Choose
Then
Under stable state
To keep Q1 ON in quasi-stable state For low current to bias Q1 , R1>>RC2 Let
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Electronic Circuit Lab Manual Design for trigger circuit: Time period Ti of trigger signal vT must be more than TON. Given that Ti=2ms. Then Choose
3. Bistable Multivibrator Given that Operation is always symmetry: then
R1>>RC1 and R2 > R1 Let
Procedure: Steps (Astable multivibrator) 1. Check the components 2. Connect the circuit diagram for symmetry waveform 3. Turn on the power supply 4. Connect the CRO channel 1probe to the Q1 collector and channel 2 to Q2
collector 5. Observe the wave forms 6. Connect the CRO channel 1probe to the Q1 base and channel 2 to Q2 base Department of ECE, VKCET
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Electronic Circuit Lab Manual 7. Observe the wave forms 8. Turn off the power supply 9. Connect the circuit diagram for asymmetry waveform 10. Repeat the steps 3 to 7 Steps (Monostable multivibrator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect th trigger signal from function generator 5. Connect the CRO channel 1probe to the Q1 collector and channel 2 to trigger
signal 6. Observe the wave forms 7. Connect the CRO channel 1probe to the Q1 base and channel 2 to trigger signal
8. Observe the wave forms 9. Connect the CRO channel 1probe to the Q2 collector and channel 2 to trigger
signal 10. Observe the wave forms 11. Connect the CRO channel 1probe to the Q2 base and channel 2 to trigger signal
12. Observe the wave forms
Steps (Bistable multivibrator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Apply set (S) and reset (R) signal via switches, observe the states of outputs
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
If Vcc =5V, VBB=10V, RC1=RC2=RC=1kΩ, R1=R2=R=50kΩ, C1=C2=.01µF. Draw the signals at vC1,vC2, vB1 and vB2. Find the frequency of oscillation. If VBB is a sinusoidal wave what is the output? 2. Design a circuit to turn ON an LED for 2 seconds and OFF for 4 seconds continuously. 3. Consider the following circuit.
Design the components for VCC =5V, βmin = 25, TON = 4seconds 4. Draw a circuit to generate a square wave. Design it for VCC =5V, βmin = 25, f=4kHz
5. Simulate the above circuits.
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Electronic Circuit Lab Manual 6. Consider the following truth table and construct a circuit using BJT to generate the logic.
Inputs Output S R Qn+1 0 0 Qn 0 1 0 1 0 1 1 1 1 7. Construct a circuit to generate the following wave.
1 0 1
Model Waveforms Astable multivibrator Symmetry waves
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Electronic Circuit Lab Manual
Asymmetr y waves
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Electronic Circuit Lab Manual
Monostable multivibrator:
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Electronic Circuit Lab Manual
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Electronic Circuit Lab Manual
Bistable multivibrator:
OBSERVATIONS: Astable Multivibrator Design parameter and components used: i)
Symmetry wave:
Given that
ii)Asymmetry wave: Given that Choose Department of ECE, VKCET
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Electronic Circuit Lab Manual
Monostable Multivibrator Design parameter and components used: Given that period of trigger signal Ti=2ms
and time
Bistable Multivibrator Given that
Wave forms: i)
Astable multivibrator (Symmetry)
ii)
Astable multivbrator (Asymmetry)
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Electronic Circuit Lab Manual iii)
Monostable multivibrator
Viva Questions: 1. Maximum frequency of oscillation of astable multivibrator is limited due to which property? 2. Give the applications of multivibrators. 3. Give the expression for the delay in trailing edge of square wave generated by astable multivibrator. 4. Define duty cycle. 5. Compare three multivibrator circuits. 6. Which circuit is referred as one-shot circuit and why? 7. Which multivibrator operates as SR flip-flop and why? 8. Which multivibrator is called free running multivibrator and why? 9. Triggering a monostable multivibrator during TON , what will happen to the
output?
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Electronic Circuit Lab Manual Expt. No. 8
OSCILLATORS Objectives: Oscillators.
a) To study the operation of Phase shift, Wien bridge, Hartley and Colpitts b) To simulate oscillator circuits using PSPICE
Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors. 7. Inductors. 8. Inductance decade box 9. Capacitance decade box 10. SL100 BJTs / BEL100N/BC107 11. Connection Wires. 12. Oscilloscope Probes. Circuit diagram: 1. RC phase shift oscillator:
Fig.1
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Electronic Circuit Lab Manual 2. Wien Bridge Oscillator:
Fig. 2(a)
Fig. 2(b)
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Electronic Circuit Lab Manual 3. Hartley Oscillator:
Fig. 3 4. Colpitts Oscillator:
Fig. 4 Department of ECE, VKCET
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Electronic Circuit Lab Manual Theory: Oscillators are circuits that produce a repetitive waveform with only a DC voltage at the output. The output waveform can be sinusoidal, rectangular, triangular, etc. At the base of almost any oscillator there is an amplification stage with a positive (regenerative ) circuit that will produce a phase shift and attenuation. Positive consists in the redirecting of the output signal to the input stage of the amplifier without a phase shift. This signal is then amplified again generating the output signal, which produces the signal. This phenomenon, in which the output signal “takes care” of itself in order to generate continuum signal is called oscillation. Two conditions then should be fulfilled to have a stable oscillator: 1. The phase shift of the loop should be 0 2. The overall gain of the loop should be 1 In order to arrive to the stable operation of the oscillator, during the starting period the gain of the loop should be greater than one, to allow the amplitude of the output signal to achieve the desired level. These conditions are called Barkhausen criteria. Sinusoidal oscillators are classified into two types: i) RC oscillators ii) LC oscillators RC oscillators use RC elements in the branch. They are useful to frequencies up to 200kHz. Two types of RC oscillators are: i) RC phase shift oscillator ii) Wien Bridge oscillator Figure 1 shows RC phase shift oscillator, which uses RC coupled amplifier as inverting amplifier and three RC networks as circuit with voltage shunt . Each RC circuit provide at least 60o phase shift, so total 180o phase shit. The gain of the network is
The frequency of oscillation is
and the current gain of the amplifier to satisfies the Barkhausen criteria is . Figure 2 shows Wien Bridge oscillator. It consists two stage RC coupled amplifier as non-inverting amplifier (360o phase shift) with voltage series negative and voltage shunt positive . Wien Bridge contains series RC and parallel RC network, while resistor element act as resistance arms of the bridge. Resistor arms provide voltage series and RC resonance arms provide voltage shunt . The bridge offer 360o phase shift at resonance frequency and the gain introduced by the network is . So the gain of the amplifier , to satisfy Barkhausen criteria. The frequency of oscillation is
. The main advantage of
this oscillator over Phase shift oscillator is its amplitude stability due to the negative . Department of ECE, VKCET
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Electronic Circuit Lab Manual LC oscillator uses amplifier with 180o phase shift and LC tuned circuit as network. These oscillators are suitable for high frequency oscillation because of it phase stability, frequency stability and less harmonics. The two familiar LC oscillators are: i) Hartley Oscillator ii) Colpitts Oscillator Figure 3 shows Hartley Oscillator circuit and it consists of a parallel LC resonator tank circuit and RC coupled amplifier. It uses a pair of tapped coils and a capacitor to produce regenerative . The output voltage is developed across and the voltage is developed across . The attenuation caused by the network
. So the gain of the amplifier,
. The tank circuit determines the
operating frequency of the Hartley oscillator and is where
,
.
Figure 4 shows Colpitts Oscillator circuit and it consists of a parallel LC resonator tank circuit and RC coupled amplifier. It uses a pair of tapped capacitors and an inductor to produce regenerative . The output voltage is developed across and the voltage is developed across . The attenuation caused by the network
. So the gain of the amplifier,
operating frequency of the oscillator and is
. The tank circuit determines the , where
. This
oscillator has better frequency stability than Hartley oscillator. Design: 1. RC Phase Shift Oscillator:
Given that For amplifier We have
(Given
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>> required
)
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Electronic Circuit Lab Manual Design for amplifier:
(or for better stability
)
(Typical value of β =100)
Design for network: Let (Designed Av > hfe)
(Use 1kΩ potentiometer to get accurate value)
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Electronic Circuit Lab Manual 2. Wien Bridge Oscillator : Given that For amplifier We have Where k ≤ 0.5
is the gain of cascade amplifier with . Then factor
Design of amplifier:
(We are using negative , so ignore the loading effect and use same design for each stage)
(Typical value of β =100)
Design of RC network for Wien Bridge:
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Electronic Circuit Lab Manual
Design for network:
Let (Use 10k pot) 3. Hartley Oscillator: Given that We have
where
And loop gain According to Barkhausen criteria Then Design for amplifier: Choose (Deg is similar to amplifier used for RC phase shift oscillator. Use low value for IC, to avoid loading effect at the input and output of the amplifier with LC tuned circuit. Low IC value provide medium matched impedances with the available L1 and L2)
Design of LC circuit: Choose L1 and L2 according to the availability and the conditions . Department of ECE, VKCET
Page 87
Electronic Circuit Lab Manual and Let L1= 10µF (Use Inductance Decade box) and L2 = 470µF (Available) Then
and is less than the gain of the amplifier
Check the conditions
at resonant frequency fo. (Where )
(If standard capacitor is not available, use Capacitance Decade box) 4. Colpitts Oscillator: Given that We have
where
And loop gain According to Barkhausen criteria Then Design for amplifier: Choose (Deg is similar to amplifier used for RC phase shift oscillator. Use low value for IC, to avoid loading effect at the input and output of the amplifier with LC tuned circuit. Low IC value provide medium matched impedances with the available C1 and C2)
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Electronic Circuit Lab Manual
Design of LC circuit: Choose C1 and C2 according to the availability and the conditions . and Let C1= 0.1µF and C2 = 0.001µF (Both are available) Check the conditions
at resonant frequency fo. (Where )
(Use Inductance Decade box) Procedure: Steps (RC phase shift oscillator) 1. Check the components 1. Connect the circuit diagram 2. Turn on the power supply 3. Connect the CRO probe to the output 4. Vary the potentiometer
to get a proper wave form
5. Observe the amplitude and frequency of output wave form
6. Change C and observe the variation in frequency of the output wave 7. Change RC and observe the variation in amplitude of the output signal
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Electronic Circuit Lab Manual 8. Connect CRO probes to the nodes of RC network and observe the 60o phase
shift signals Steps (Wien Bridge oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the potentiometer
to get a proper wave form
6. Observe the amplitude and frequency of output wave form 7. Change C and observe the variation in frequency of the output wave Steps (Hartley oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the inductance decade box to the desired value
6. Observe the amplitude and frequency of output wave form 7. Change C and observe the variation in frequency of the output wave Steps (Colpitts oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the inductance decade box to the desired value 6. Observe the amplitude and frequency of output wave form Department of ECE, VKCET
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Electronic Circuit Lab Manual 7. Change L and observe the variation in frequency of the output wave
Pre-lab Assignments: 1. Design RC network of RC phase shift oscillator for frequency 20kHz. 2. Design RC network of Wien bridge oscillator for frequency 15kHz. 3. Design tuned circuit of Hartley oscillator for frequency 500kHz. 4. Design tuned circuit of Colpitts oscillator for frequency 750kHz. 5. Compare phase shift oscillators and tuned oscillators. 6. Define frequency and amplitude stabilization used in oscillators. Model Waveforms Phase Shift Oscillators
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Electronic Circuit Lab Manual Tuned Oscillators
Simulated Results: a) RC Phase Shift Oscillator
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Electronic Circuit Lab Manual b) Wien Bridge Oscillator
(Only real time simulation using virtual oscilloscope is possible. SPICE simulation is not possible !) c) Hartley Oscillator
d) Colpitts oscillator
(To simulate inductors using SPICE, connect a low resistance of value 10mΩ in series with it.)
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Electronic Circuit Lab Manual OBSERVATIONS: 1. RC Phase Shift Oscillator: Design parameters and components used: Given that For amplifier
(Use 1kΩ potentiometer to get accurate value) Wave form:
2. Wien Bridge Oscillator :
Design parameters and components used: Given that For amplifier
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Electronic Circuit Lab Manual (Use 10k pot) Wave form:
3. Hartley Oscillator:
Design parameters and components used: Given that For amplifier
L1= 10µF L2 = 470µF Wave form:
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Electronic Circuit Lab Manual 4. Colpitts Oscillator: Design parameters and components used: Given that For amplifier
C1= 0.1µF C2 = 0.001µF (Use Inductance Decade box) Wave form:
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Electronic Circuit Lab Manual Expt. No. 9 SCHMITT TRIGGER Objective: To study the operation of Schmitt trigger circuit using BJT. Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. SL100 BJTs / BEL100N/BC107 7. Connection Wires. 8. Oscilloscope Probes. Circuit diagram:
Fig. 1
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Electronic Circuit Lab Manual Theory: Schmitt trigger is a threshold circuits with positive having a loop gain > 1. The circuit is named "trigger" because the output retains its value until the input changes sufficiently to trigger a change: in the non-inverting configuration, when the input is higher than a certain chosen threshold (UTP), the output is high; when the input is below a different (lower) chosen threshold (LTP), the output is low; when the input is between the two, the output retains its value. This dual threshold action is called hysteresis and implies that the Schmitt trigger possesses memory and can act as a bistable circuit (latch). There is a close relation between the two kinds of circuits that actually are the same: a Schmitt trigger can be converted into a latch and v.v., a latch can be converted into a Schmitt trigger. Design: Given that Upper threshold point voltage
Choose
(Determines voltage drop at output when Q2 is ON, so keep a low value)
Lower threshold point voltage
Choose Department of ECE, VKCET
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Electronic Circuit Lab Manual Procedure: Steps 1. Check the components 2. Connect the circuit 3. Turn on power supply, apply input signal (10Vpp, 1kHz).
4. Connect CRO channel 1 (Y) probe to output and channel 2 (X) probe to input 5. Observe input and output wave 6. Put the CRO in XY mode and observe the hysteresis 7. Observe output for different input signal by changing signal mode of function generator. 8. Turn off power supply 9. Connect variable dc source to the input 10. Turn on power supply. 11. Vary input dc voltage from 0V to 4V, note down the change in output for VUT 12. Vary input dc voltage from 4V to 0V, note down the change in output for VLT
Pre-lab Assignments: •
Consider the circuit shown in fig.1. Find the Hysteresis voltage of the circuit, if
•
For the input wave shown below, plot the output wave for the circuit in fig.1.
Where Vm=10V Department of ECE, VKCET
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Electronic Circuit Lab Manual Model Waveforms Input and Output waveforms:
Hysteresis Curve
Hysteresis Voltage VH = VUT - VLT = 2V Tabular Column a)
For UTP Vin (V) 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4
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Vo (V)
Page 100
Electronic Circuit Lab Manual b) For LTP Vin (V) Vo (V) 4 3.6 3.2 2.8 2.4 2 1.6 1.2 .8 0.4 0 (Observe the hysteresis curve on oscilloscope by applying V in as X-axis signal and Vo as Yaxis signal. Put oscilloscope in XY mode) OBSERVATIONS: Given parameters and components used: Given that
Input and output wave forms:
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SERIES VOLTAGE REGULATOR Objective: Aim of the experiment is to understand the operation of simple series voltage regulator Equipments and Components Required: 1. Digital Multimeters (DMM). 2. DC power supply. 3. Project Breadboard. 4. Resistors. 5. BC107 BJT 6. Zener diode. 7. Connection Wires. Circuit Diagram:
Design: Given that Vo = 15V, ILmin = 1mA, ILmax = 100mA, Vin min = 16V, Vin max = 30V, IZ max = 100mA and β = 100 Optimum value of Optimum value of
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and and
Page 1
Electronic Circuit Lab Manual Procedure: 1. Test all components 2. Connect the circuit diagram 3. Connect the variable dc power supply as input and turn on. 4. Vary the input voltage from 0 to 30V and note down the corresponding output voltage
using voltmeter for line regulation 5. Turn off the power supply 6. Replace RL with 100k pot in series with RLmin
7. Turn on power supply and set it to 20V 8. Vary the pot from higher position to lower position, note down the output voltage using voltmeter and load current using ammeter for load regulation Pre-Lab Assignments: 1. If 15Vpp sinusoidal input voltage is applied to the circuit shown above, sketch the output waveform. 2.
If the input Vin = 10V and R1 = 10kΩ , calculate I1 and IZ, where VZ = 5.2V and β =
50. 3.
If R1 reduces what is the improvement of the circuit?
4.
Derive the expression for Vo of the circuit shown in fig.1
5.
Find optimum value of R1.
6.
How does changing RL affect Vo?
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Page 2
Electronic Circuit Lab Manual Model Characteristics: Line Regulation:
Load Regulation
OBSERVATIONS Design parameters and components used: Vo = 15V, ILmin = 1mA, ILmax = 100mA, Vin min = 16V , Vin max = 30V, IZ max = 100mA and β = 100 (For maximum current) 10Ω to 1.5k Ω
(For minimum current)
Tabular Column Line regulation RLmax=15kΩ, R1max=1.5kΩ Vin(V) 0 1 2 3 4 5 6 7 8 9 10 11 12 14 15 16 17 18 20 30
Vo(V) 0 1.3 1.2 2.2 3.2 4.1 5.1 5.9 6.9 7.9 8.8 9.8 10.5 12.2 13.2 14 14.4 14.6 14.6 14.6
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Electronic Circuit Lab Manual Load regulation Vin = 30V, RLmin = 150Ω IL(mA) Vo(V) 0 15 1 14.8 2 14.7 4 14.7 7 14.7 8 14.7 9 14.7 10 14.7 50 14.7
Viva Questions:: 1. Define regulation. List out different types of regulators. 2. Define line and load regulation. 3. What is percentage of voltage regulation? 4. Compare different types of regulators. 5. Draw the basic block diagram of series voltage regulator.
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Electronic Circuit Lab Manual Expt. No. 2
POWER AMPLIFIERS Objective: The aim of the experiment is to study the operation and efficiency of Class B and Class AB power amplifiers Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100, SK100 BJTs 1N4007 Diodes Connection Wires. Oscilloscope Probes.
Circuit diagram: Class B Power Amplifier:
Fig. 1 Department of ECE, VKCET
Page 5
Electronic Circuit Lab Manual Theory: Class B circuit provides an output signal varying over one-half the input signal cycle, or for 180° of signal. The dc bias point for class B is therefore at 0 V, with the output then varying from this bias point for a half cycle. Obviously, the output is not a faithful reproduction of the input if only one half-cycle is present. Two class B operations—one to provide output on the positive output half-cycle and another to provide operation on the negative-output half-cycle are necessary. The combined half-cycles then provide an output for a full 360° of operation. This type of connection is referred to as push-pull operation. An amplifier may be biased at a dc level above the zero base current level of class B and above one-half the supply voltage level of class A; this bias condition is class AB. Class AB operation still requires a push-pull connection to achieve a full output cycle, but the dc bias level is usually closer to the zero base current level for better power efficiency. For class AB operation, the output signal swing occurs between 180° and 360° and is neither class A nor class B operation. Following figure shows a diagram for push-pull operation.
An ac input signal is applied to the push-pull circuit, with each half operating on alternate half-cycles, the load then receiving a signal for the full ac cycle. The power transistors used in the push-pull circuit are capable of delivering the desired power to the load, and the class B operation of these transistors provides greater efficiency than was possible using a single transistor in class A operation. DC Analysis: The dc power supplied to the load by an amplifier is given by
AC Analysis: Output power is given by The efficiency of Class B amplifier can be calculated by Maximum η of Class B operation is given by 78.5% The power dissipated by the individual output transistor is given by
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Page 6
Electronic Circuit Lab Manual Design: Given that The transistors are as emitter follower.
Output power,
Input power, Efficiency, Power dissipation by each transistor, For R1: Under dc conditions,
and To keep transistor at cut-off region under dc biased condition I1 should be low.
And
.
For R2: Class B operation R2 should be negligible. Use the equation Department of ECE, VKCET
. Page 7
Electronic Circuit Lab Manual
Choose For Class AB operation
or replace the resistors with diodes
Choose Note: Try to observe the output for different R2 For coupling capacitors:
Choose
and
Procedure: Steps: 1. Check the components 2. Connect the circuit (use R1 for class B operation) 3. Turn on the power supply and apply input signal vin (1Vpp) from function generator
4. Connect CRO probes channel 1 to input and channel 2 to output 5. Observe the input and output wave forms and measure I dc by setting vin =0V and Io
vin=1Vpp, also measure corresponding Vo 6. Turn off the power supply 7. Replace R1 for Class AB operation
8. Turn on power supply 9. Observe the input and output wave forms and measure I dc by setting vin =0V and Io
vin=1Vpp, also measure corresponding Vo Department of ECE, VKCET
Page 8
Electronic Circuit Lab Manual Pre-lab Assignments: 1. What is the ideal DC value of the output signal of Class B and Class AB amplifier if there is no input? Compare this with Class A amplifier. 2. Plot one of the collector current (I ) vs. time, is it full-wave of half-wave? 3. Derive expressions for of Class B power amplifier. 4. List out the advantages and disadvantages of Class A, Class B, Class AB power, Class C and Class D amplifiers. C
5. Design the circuits shown in fig.1 for
, β =100,
and draw the output wave form for sinusoidal input. Model Waveforms: Class B power amplifier:
Class AB power amplifier:
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Electronic Circuit Lab Manual Simulated Results: Efficiency: Class B Power Amplifier: R1=24kΩ (If it is very high, η can be increased to ideal value), R2=100Ω , RMS current delivered from source during the operation
Class AB Power Amplifier (R2=10k ) : , RMS current delivered from source during the operation
OBSERVATIONS Design parameters and components used:
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Electronic Circuit Lab Manual Input and Output waveforms: Class B
Class AB
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Electronic Circuit Lab Manual
Efficiency Class B
(?) Not satisfied. This is due to the lack of true RMS meter Class AB
(?) Not satisfied. This is due to the lack of true rms meter Viva Questions: 1. Differentiate Voltage Amplifiers and Power Amplifiers. 2. Classify Power amplifiers. Department of ECE, VKCET
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Electronic Circuit Lab Manual 3. Define efficiency of Power Amplifiers. 4. Suggest a way (with a diagram) how you might be able to improve the biasing to eliminate the crossover distortion. 5. How you might reduce distortion by using a negative ? 6. What is the practical application of power amplifiers?
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Electronic Circuit Lab Manual Expt. No. 3
DIFFERENTIAL AMPLIFIER USING BJT Objective: The aim of the experiment is to study the operation of differential amplifiers using BJT and obtain CMRR and input resistance. Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors 7. Diodes 1N4007 8. BC 107 or SL100 BJTs 9. Connection Wires. 10. Oscilloscope Probes. Circuit diagram: a) Differential Amplifier using BJT: i)
Differential Mode, Balanced Output (for differential gain)
Fig. 1
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Electronic Circuit Lab Manual ii)
Common mode, balanced output (for common mode gain)
Fig. 2 Different Modes: a) Dual input balanced output The circuit is same as shown in Fig. 1 b) Dual input unbalanced output The input is same as above, but output is taking across any of the transistor’s collector and ground. c) Single input balanced output. One of the inputs set to ground and output is same as first mode. d) Single input unbalanced output. One of the inputs set to ground and output is same as second mode.
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Electronic Circuit Lab Manual Power Supply Arrangement for Dual Voltage Source:
Fig. 3 Note: For unbalanced output use coupling capacitor at the output Theory: The differential amplifier, or differential pair, is an essential building block in all integrated amplifiers. In general, the input stage of any anategrated circuit with more than one input consists of a differential pair or differential amplifier. The basic differential pair circuit consists of two-matched transistors Q1and Q2 , whose emitters are ed together and biased by the constant current source circuit. Q1, D1, D2, R2 and RE acts as current source, which introduce constant current IEE to the differential amplifier with high ac source resistance, since ac equivalent of this dc current source is ideally open circuit. The important characteristics of the differential amplifier are: the common-mode rejection ratio CMRR, the input differential resistance R id, and the differential-mode gain Ad. Differential gain: , where Vid is differential input voltage,
and Vod is differential
output. For a perfectly matched pair transistor differential gain should be infinite.
CMRR: Common Mode Rejection Ratio, and it is
, where Vcm is common mode input voltage,
, where Ac is common mode gain and Voc is common
mode output. For perfectly matched pair transistor common mode gain should be zero, and then CMRR should be infinite. Differential input resistance: The resistance between the differential input and ideally it should be infinite.
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Electronic Circuit Lab Manual DC Analysis:
For constant current source circuit:
AC Analysis: Balanced output Mode: Differential gain Common mode gain CMRR Differential mode input resistance Output resistance Unbalanced output Mode: Differential gain Common mode gain CMRR Differential mode input resistance Output resistance Resistance of current source circuit:
Design: Given that From data sheet of BC 107,
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,
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Electronic Circuit Lab Manual
From the above design:
,
Procedure: Steps 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply and apply differential input signals v 1 and v2 using
function generator 4. Connect CRO probe of channel 1 to one input and channel 2 to unbalanced
output vo1 via a coupling capacitor, observe the differential input and output for differential gain 5. Repeat the above step for other vo2
6. Connect channel 2 probe across the collector of transistors without coupling capacitors 7. Observe the balanced output voltage for differential gain 8. Apply same signal to the two inputs as common mode input 9. Repeat step 6 and observe input and output for common mode gain Department of ECE, VKCET
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Define CMRR. 2. Draw the basic circuit of differential amplifier using BJT. Give the significance of
RC and REE 3. Design differential amplifier with current source circuit using BJT using the following specifications 4.
5. Give the use of current mirror circuit in differential amplifier. 6. Give the advantages of MOSFET differential amplifier. 7. Design differential amplifier with current source circuit using MOSFET using the following specifications
8. Draw the differential amplifier circuit using BJT with active load. Model Waveforms: Differential Input and Balanced Output
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Electronic Circuit Lab Manual Differential Input and Unbalanced Output
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Electronic Circuit Lab Manual Common Mode Input Unbalanced Output
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Electronic Circuit Lab Manual Simulated Results: Differential Gain: For balanced output:
For unbalanced output:
Common Mode Gain:
OBSERVATIONS Design parameters and components used:
From data sheet of BC 107,
,
Differential Mode: Input and output wave forms:
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Electronic Circuit Lab Manual i)
Balanced output:
ii)
Unbalanced output:
Common Mode: Input and output wave forms:
i)
Balanced output:
Viva Questions: 1) Define differential amplifier and give its application 2) Draw a current mirror circuit. Differentiate it with constant current source. 3) In a differential amplifier |VCC| ≠ |VEE|, list out the problems
4) Differentiate different configurations of differential amplifiers. Which one is commonly used? 5) Give the main advantage of constant current bias over emitter bias. Department of ECE, VKCET
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Electronic Circuit Lab Manual Expt. No. 4
CASCADE AMPLIFIER Objective: The aim of the experiment is to study the operation of cascade amplifier and obtain the frequency response and bandwidth Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100 BJTs Connection Wires. Oscilloscope Probes.
Circuit diagram:
Fig. 1
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Electronic Circuit Lab Manual Theory: A single stage of amplification is not enough for a particular application. The overall gain can be increased by using more than one stage, so when two amplifiers are connected in such a way that the output signal of the first serves as the input signal to the second, the amplifiers are said to be connected in cascade. The most common cascade arrangement is the common-emitter RC coupled cascade amplifier. Common-emitter amplifier exhibit high voltage, high current, and high power gains, so they are very familiar than other configurations. Multistage amplifiers can be used either to increase the overall small signal voltage gain, or to provide an overall voltage gain greater than 1, with a very low output resistance. Figure 1 shows an RC-coupled cascaded amplifier. Capacitors C1 and C2 couple the signal into Q1 and Q2, respectively. C3 is used for coupling the signal from Q 2 to its load. If the operation of coupled amplifiers is considered, a complicating factor appears. The addition of a second stage may alter the characteristics of the first stage and thus affect the level of signal fed to the second stage. To compute the overall gain of the amplifier, it is easier to calculate unloaded voltage gain for each stage, then including the loading effect by computing voltage dividers for the output resistance and input resistance of the following stage. This idea is illustrated in figure 2. Each transistor is drawn as an amplifier consisting of an input resistance R in , an output resistance, Rout along with its unloaded gain, AV(NL).
Fig. 2
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Electronic Circuit Lab Manual Then, the overall loaded gain A V , of this amplifier can be found by:
For the RC Coupled (CE - CE) multistage amplifier with CE:
and Note that if a load resistor was added across the output, an additional voltage divider consisting of the output resistance of the second stage and the added load resistor is used to compute the new gain. If
and
DC Analysis: For 1st stage amplifier:
Where,
and
Stability factor For 2nd stage amplifier the analysis is same.
AC Analysis: For 1st stage amplifier: Voltage gain,
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Electronic Circuit Lab Manual Input resistance, Output resistance, For 2 stage amplifier: Voltage gain, nd
Input resistance, Output resistance, Design: Given that
For 2nd stage amplifier:
For
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Electronic Circuit Lab Manual From the above design
, where
For 1st stage amplifier:
For
From the above design
, where
For capacitors:
Where
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Electronic Circuit Lab Manual
Procedure: Steps 1. Check the components 2. Connect the circuit diagram for second stage amplifier 3. Turn on the power supply, apply input signal of voltage 10mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz)
6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note
down the corresponding output voltage for plotting frequency response 8. Turn off the power supply and construct first stage of amplifier and coupled its output to second stage. 9. Turn on the power supply, apply input signal of voltage 1mVpp (low voltage) to the input using function generator 10. Repeat the steps 4 to 7 Pre-lab Assignments: 1. Find the Q-point of each stage of the circuit shown in fig.1, where R 1 = R3 =
20kΩ, R2 = R4 = 10kΩ, RE1=RE2= 1kΩ, RC1=4kΩ, RC2=1kΩ VCC = 15V, VCE1= VCE2=0.2V, VBE1= VBE2=0.6V 2. Re-design the components of the circuit shown in fig. 1 for fL=1kHz
3. Define Power gain, Voltage gain and Current gain. How it represent in dB? Department of ECE, VKCET
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Electronic Circuit Lab Manual 4. What is transition frequency of transistor? Give the typical value for the given
transistor. 5. Simulate the circuit given in experiment using SPICE. Compare designed and simulated dc biasing conditions, show input and its corresponding output wave forms, plot frequency response and compare it with designed values. Model Waveforms: Input Wave form:
Output Waveforms (1st stage and 2nd stage):
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Electronic Circuit Lab Manual Tabular Column: For Single Stage Amplifier:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Av in dB
For Two Stage Amplifier:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Av in dB
Simulated Results:
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Electronic Circuit Lab Manual First Stage Mid band gain = 21.9dB Lower cutoff frequency fL = 192Hz Upper cutoff frequency fH = 4.3MHz Bandwidth = 4.3MHz Multi stage Mid band gain = 46.3dB Lower cutoff frequency fL = 257Hz Upper cutoff frequency fH = 4.15MHz Bandwidth = 4.15MHz OBSERVATIONS Design parameters and components used:
Input and output waveforms: Single stage:
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Electronic Circuit Lab Manual Two stage:
Tabular column: Single stage amplifier
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Two Stage Amplifier:
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Viva Questions: 7. What are the requirements of biasing and coupling circuits in BJT amplifiers? 8. What is the use of CE in RC coupled amplifier and give its influence in frequency response? 9. Give the advantages and disadvantages of cascade amplifier. 10. What is half-power frequency? 11. In amplifiers, why mid frequency gain is independent to frequency? 12. What is bode-plot? 13. What is the method to increase the output voltage swing of an amplifier? 14. How load resistances influence the gain of BJT amplifiers? 15. What is SPICE?
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Electronic Circuit Lab Manual Expt. No. 5
CASCODE AMPLIFIER Objectives: a) To study the operation of cascode amplifier using BJT and obtain the frequency response and bandwidth. b) To simulate cascode amplifier circuit using SPICE. Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. BEL100N BJTs Connection Wires. Oscilloscope Probes.
Circuit diagram: a) Cascode amplifier using BJT
Fig. 1
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Electronic Circuit Lab Manual Theory: The bandwidth of CE amplifier is limited due to the Miller capacitance effect at high frequency operation. This can be overcome by using adding a second stage CB amplifier (direct coupling with CE stage). This arrangement is called cascode amplifier. This amplifier has high bandwidth due to the reduction in Miller capacitance effect. The gain of the amplifier is high due the overall gain of CE and CB stage. The circuit has an input characteristics of CE amplifier and output characteristics of CB amplifier. In fig.1 R1, R2, and R3 form biasing network for Q1 and Q2; C1 and C3 for coupling ac signals; C2 and CE for bying resistors R2 and RE, respectively at ac signals. Transistors Q1 and Q2 should be identical DC Analysis:
AC Analysis: Voltage gain, Current gain,
, where
Input resistance, Output resistance, Design: Given that Find typical value of β from the data sheet of BEL100N.
(To get maximum output swing keeps Q1 collector voltage low) (To get maximum output swing keeps Q2 collector voltage 50% of VCC) Department of ECE, VKCET
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Electronic Circuit Lab Manual
Procedure: Steps 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply, apply input signal of voltage 10mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz) 6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response Department of ECE, VKCET
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
Where
. Find Voltage gain, Current gain Input impedance and Output impedance of the circuit 2. Simulate the above circuit (use
using SPICE and submit: a) Circuit diagram with dc bias voltages, b) Input and output wave forms and c) Frequency response curve
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Electronic Circuit Lab Manual Model Waveforms: Input Wave form:
Output Waveform:
Tabular Column:
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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log10f
Av in dB
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Electronic Circuit Lab Manual Simulated Results:
Mid band gain =37.2dB Lower cutoff frequency fL = 752 kHz Higher cutoff frequency fH = 24MHz Bandwidth = 25.8MHz OBSERVATIONS Design parameters and components used: Given that
Input and output wave forms
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Electronic Circuit Lab Manual Tabular Column:
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Viva Questions: 9. Define miller effect. 10. Say the advantages and disadvantages of CE, CC and CB configuration of BJT. 11. How the bandwidth improved in cascode amplifier? 12. Which multistage amplifier has maximum bandwidth? 13. Give the expression for current gain of cascode amplifier using BJT. 14. What are the applications of cascode amplifier? 15. In an amplifier which factors limits gain at low and high frequencies?
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Electronic Circuit Lab Manual Expt. No. 6
FEED BACK AMPLIFIERS Objectives: a) To study the operation of voltage series negative amplifier and obtain the frequency response and bandwidth b) To study the operation of current series negative amplifier and obtain the frequency response and bandwidth Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors. 7. SL100 BJTs / BEL100N/BC107 8. Connection Wires. 9. Oscilloscope Probes. Circuit diagram: a) Voltage series negative amplifier i)
Without feed back
Fig.1 Department of ECE, VKCET
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Electronic Circuit Lab Manual ii)
With
Fig. 2 b) Current series negative amplifier: i)
Without
Fig. 3
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Electronic Circuit Lab Manual ii)
With
Fig. 4 Theory: A amplifier is one in which the output signal is sampled and fed back to the input to form an error signal that drives the amplifier. The basic block diagram of amplifier is shown below.
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Electronic Circuit Lab Manual The input signal, Vs, is applied to a mixer network, where it is combined with a signal, Vf. The difference of these signals, Vi, is then the input voltage to the amplifier. A portion of the amplifier output, Vo, is connected to the network of gain k, which provides a reduced portion of the output as signal to the input mixer network. If the signal is of opposite polarity to the input signal, negative results otherwise positive . The advantages of negative are: 1. Higher input impedance. 2. Better stabilized voltage gain. 3. Improved frequency response. 4. Lower output impedance. 5. Reduced noise. 6. More linear operation. Four basic types of connections along with the properties are given below:
Series-Shunt (Voltage-Series) Shunt-Shunt (Voltage-Shunt) Series-Series (Current-Series) Shunt-Series (Current-Shunt) In the list above, voltage refers to connecting the output voltage as input to the network; current refers to tapping off some output current through the network. Series refers to connecting the signal in series with the input signal voltage; shunt refers to connecting the signal in shunt (parallel) with an input current source. Series connections tend to increase the input resistance, while shunt connections tend to decrease the input resistance. Voltage tends to decrease the output impedance, while current tends to increase the output impedance. The gain and factor of four configurations are given below:
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Electronic Circuit Lab Manual a) Voltage Series Figure 2 show two-stage RC coupled amplifier cascaded with voltage series . The cascade amplifier gain with input loop and it opposes
, gain
. The part of output voltage (
and gain is to the
and results voltage series negative . If
,
the amplifier gain is b) Current Series Figure 4 show single stage RC coupled amplifier with current series . The gain of the amplifier without (with CE) . The element is RE . The gain of the amplifier with current
is fed back to the input (
opposes the input voltage
. Here the output ) is fed back to the input and it
. The gain of the circuit is
Design: a) Voltage series amplifier: Given that
For 2nd stage amplifier:
For
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Electronic Circuit Lab Manual
From the above design
, where
For 1st stage amplifier:
For
From the above design
, where
For capacitors:
Where
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Electronic Circuit Lab Manual
For obtaining higher cutoff frequency: where
and
(considering first stage)
From datasheet
For network:
Let
From the above design theoretical values of: Voltage gain with
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Electronic Circuit Lab Manual Lower cutoff frequency without Lower cutoff frequency with b) Current series amplifier: Given that
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Electronic Circuit Lab Manual
From the above design theoretical values of: Voltage gain with , Conductance Gain without Conductance Gain with Lower cutoff frequency without Lower cutoff frequency with Procedure: Steps (Voltage series ) 2. Check the components 3. Connect the circuit diagram without 4. Turn on the power supply, apply input signal of voltage 2mVpp (low voltage) to the
input using function generator 5. Connect CRO channel 1 probe to input and channel 2 to output. 6. Adjust the input signal frequency to mid band (10kHz) 7. Observe the input and output signal and measure the mid band gain 8. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response 9. Turn off the power supply. 10. Connect the circuit 11. Turn on the power supply, apply input signal of voltage 10mVpp to the input using
function generator 12. Connect CRO channel 1 probe to input and channel 2 to output. 13. Adjust the input signal frequency to mid band (10kHz) Department of ECE, VKCET
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Electronic Circuit Lab Manual 14. Observe the input and output signal and measure the mid band gain 15. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response Steps (Current series ) 1. Check the components 2. Connect the circuit diagram without 3. Turn on the power supply, apply input signal of voltage 2mVpp (low voltage) to the input using function generator 4. Connect CRO channel 1 probe to input and channel 2 to output. 5. Adjust the input signal frequency to mid band (10kHz) 6. Observe the input and output signal and measure the mid band gain 7. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response 8. Turn off the power supply. 9. Connect the circuit (Remove CE )
10. Turn on the power supply, apply input signal of voltage 10mVpp to the input using function generator 11. Connect CRO channel 1 probe to input and channel 2 to output. 12. Adjust the input signal frequency to mid band (10kHz) 13. Observe the input and output signal and measure the mid band gain 14. Vary input signal frequency from 10Hz to 3MHz (in decade roll-off rate), note down the corresponding output voltage for plotting frequency response
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
If
Find a) factor b) Voltage gain without and with c) Input impedance without and with d) Output impedance without and with 2. Simulate the circuits shown in fig.1 to fig.2. Submit the following: a) Input and output waveforms b) Frequency response.
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Electronic Circuit Lab Manual
3. Consider the following circuit.
Find bandwidth of the circuit where
Model Waveforms and Frequency Response: Voltage Series Amplifier without : Input Wave form and Output Waveforms:
vin=2mVpp vo = 356mVpp Department of ECE, VKCET
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Electronic Circuit Lab Manual Frequency response:
Voltage Series Amplifier with : Input Wave form and Output Waveforms:
vin=20mVpp, vo = 28.8mVpp Frequency response:
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Electronic Circuit Lab Manual Current Series Amplifier without : Input Wave form and Output Waveforms:
vin=20mVpp vo = 5Vpp Frequency response:
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Electronic Circuit Lab Manual Current Series Amplifier with : Input Wave form and Output Waveforms:
vin=10mVpp, vo 25mVpp Frequency response:
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Electronic Circuit Lab Manual Tabular Column: Voltage Series Amplifier without :
Input Signal Frequency, f (Hz)
Output Voltage Voltage, Gain, Av vo (vpp)
Av in dB
Voltage Series Amplifier with :
Input Output Voltage Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Current Series Amplifier without :
Input Output Voltage Av in dB Signal Voltage, Gain, Frequency, vo (vpp) Av f (Hz)
Voltage Series Amplifier with :
Input Output Voltage Signal Voltage, Gain, Av Frequency, vo (vpp) f (Hz)
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Av in dB
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Electronic Circuit Lab Manual Simulated Results: a) Voltage Series without :
Mid band gain = 45dB Lower cutoff frequency fL = 1.21kHz Upper cutoff frequency fH =4.33MHz Bandwidth = 4.32MHz b) Voltage Series with :
Mid band gain = 32.4dB Lower cutoff frequency fL = 931Hz Upper cutoff frequency fH = 5.48MHz Bandwidth = 5.479MHz c) Current Series without :
Mid band gain = 46.3dB Lower cutoff frequency fL = 1.12kHz Upper cutoff frequency fH =2.46MHz Bandwidth = 2.458MHz d) Currente Series with :
Mid band gain = 6.25dB Lower cutoff frequency fL = 816Hz Upper cutoff frequency fH = 12.2MHz Bandwidth = 12.2MHz OBSERVATIONS Voltage Series : Design parameters and components used:
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Electronic Circuit Lab Manual
For network:
Input and output wave forms: i)
Without
ii)
With
Tabular Column: i)
Without
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
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Voltage Gain, Av
Av in dB
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Electronic Circuit Lab Manual ii)
With
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Current Series : Design parameters and components used:
Input and output wave forms: i)
Without
ii) With
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Electronic Circuit Lab Manual Tabular Column: i)
Without
Input Signal Frequency, f (Hz)
ii)
Output Voltage, vo (vpp)
Voltage Gain, Av
Av in dB
Voltage Gain, Av
Av in dB
With
Input Signal Frequency, f (Hz)
Output Voltage, vo (vpp)
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Electronic Circuit Lab Manual Viva Questions: 1. What are the types of mixing and sampling used in voltage series and current series ? 2. What is the effect of on the input and output resistances in various ? 3. What is the effect of negative ? 4. Show that the gain with is independent of amplifier parameters. 5. What is meant by gain de-sensitivity?
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Electronic Circuit Lab Manual Expt. No. 7
MULTIVIBRATORS Objectives:
a) To study the operation of astable, monostable and bistable multivibrators b) To simulate multivibrator circuits using PSPICE
Components and equipments required: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Oscilloscope (Scope/CRO). Function Generators (FG). DC power supply. Project Breadboard. Resistors. Capacitors. SL100 BJTs / BEL100N/BC107 Connection Wires. Oscilloscope Probes.
Circuit diagram: a) Astable multivibrator:
Fig.1
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Electronic Circuit Lab Manual b) Monostable multivibrator:
Fig. 2 c) Bistable multivibrator
Fig. 3
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Electronic Circuit Lab Manual Theory: Multivibrators are switching circuits and switches between a "HIGH" state and a "LOW" state producing a continuous output. They can be used as oscillators, timers and flip-flops. The circuit can be characterized by two amplifying devices (transistors) cross-coupled by resistors or capacitors. There are basically three types of multivibrator circuits: Astable - A free-running multivibrator that has NO stable states but switches continuously between two states this action produces a train of square wave pulses at a fixed frequency. Monostable - A one-shot multivibrator that has only ONE stable state and is triggered externally with it returning back to its first stable state. Bistable - A flip-flop that has TWO stable states that produces a single pulse either positive or negative in value. Fig. 1 shows the circuit diagram of astable multivibrator. The circuit has two stable states that change alternatively with maximum transition rate because of the "accelerating" positive . It is implemented by the coupling capacitors C1 and C2 that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. In each state, one transistor is switched on and the other is switched off. Accordingly, one fully charged capacitor discharges (reverse charges) slowly thus converting the time into an exponentially changing voltage. At the same time, the other empty capacitor quickly charges thus restoring its charge (the first capacitor acts as a time-setting capacitor and the second prepares to play this role in the next state). The circuit operation is based on the fact that the forward-biased base-emitter junction of the switched-on bipolar transistor can provide a path for the capacitor restoration. The switching periods of each transistor are time
period
and
frequency
of
square
. Thus output
at
collector
of
transistor
is
where Figure 2 shows the circuit diagram of monostable multivibrator with trigger circuit. In this one resistive-capacitive network is replaced by a resistive network (just a resistor). The Department of ECE, VKCET
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Electronic Circuit Lab Manual circuit can be thought as a half astable multivibrator. When triggered by an input pulse, a monostable multivibrator will switch to its unstable position for a period of time, and then return to its stable state. The time period monostable multivibrator remains in unstable state is given by (at collector output of Q2 or
at collector of Q1). If repeated
application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable. If further trigger pulses do not affect the period, the circuit is a non-retriggerable multivibrator. In the bistable multivibrator (shown in Figure 3), both the resistive-capacitive network are replaced by resistive networks (just resistors or direct coupling).This latch circuit is similar to an astable multivibrator, except that there is no charge or discharge time, due to the absence of capacitors. Hence, when the circuit is switched on, if Q1 is on, its collector is at 0 V. As a result, Q2 gets switched off. This results in more than half +V volts being applied to R4 causing current into the base of Q1, thus keeping it on. Thus, the circuit remains stable in a single state continuously. Similarly, Q2 remains on continuously, if it happens to get switched on first. Switching of state can be done via Set (S) and Reset (R) terminals connected to the bases. For example, if Q1 is on and Set is grounded momentarily, this switches Q 1 off, and makes Q2 on. Thus, Set is used to "set" Q2 on, and Reset is used to "reset" it to off state. Design: 1. Astable multivibrator: i) Symmetry wave: Given that For symmetrical wave We have
Choose Then Department of ECE, VKCET
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Electronic Circuit Lab Manual Base current Collector current Condition for oscillation
and
For that
ii) Asymmetry wave: Given that We have Choose
Then
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Electronic Circuit Lab Manual 2. Monostable multivibrator: Given that trigger signal Ti=2ms
and time period of
Choose
Then
Under stable state
To keep Q1 ON in quasi-stable state For low current to bias Q1 , R1>>RC2 Let
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Electronic Circuit Lab Manual Design for trigger circuit: Time period Ti of trigger signal vT must be more than TON. Given that Ti=2ms. Then Choose
3. Bistable Multivibrator Given that Operation is always symmetry: then
R1>>RC1 and R2 > R1 Let
Procedure: Steps (Astable multivibrator) 1. Check the components 2. Connect the circuit diagram for symmetry waveform 3. Turn on the power supply 4. Connect the CRO channel 1probe to the Q1 collector and channel 2 to Q2
collector 5. Observe the wave forms 6. Connect the CRO channel 1probe to the Q1 base and channel 2 to Q2 base Department of ECE, VKCET
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Electronic Circuit Lab Manual 7. Observe the wave forms 8. Turn off the power supply 9. Connect the circuit diagram for asymmetry waveform 10. Repeat the steps 3 to 7 Steps (Monostable multivibrator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect th trigger signal from function generator 5. Connect the CRO channel 1probe to the Q1 collector and channel 2 to trigger
signal 6. Observe the wave forms 7. Connect the CRO channel 1probe to the Q1 base and channel 2 to trigger signal
8. Observe the wave forms 9. Connect the CRO channel 1probe to the Q2 collector and channel 2 to trigger
signal 10. Observe the wave forms 11. Connect the CRO channel 1probe to the Q2 base and channel 2 to trigger signal
12. Observe the wave forms
Steps (Bistable multivibrator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Apply set (S) and reset (R) signal via switches, observe the states of outputs
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Electronic Circuit Lab Manual Pre-lab Assignments: 1. Consider the following circuit.
If Vcc =5V, VBB=10V, RC1=RC2=RC=1kΩ, R1=R2=R=50kΩ, C1=C2=.01µF. Draw the signals at vC1,vC2, vB1 and vB2. Find the frequency of oscillation. If VBB is a sinusoidal wave what is the output? 2. Design a circuit to turn ON an LED for 2 seconds and OFF for 4 seconds continuously. 3. Consider the following circuit.
Design the components for VCC =5V, βmin = 25, TON = 4seconds 4. Draw a circuit to generate a square wave. Design it for VCC =5V, βmin = 25, f=4kHz
5. Simulate the above circuits.
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Electronic Circuit Lab Manual 6. Consider the following truth table and construct a circuit using BJT to generate the logic.
Inputs Output S R Qn+1 0 0 Qn 0 1 0 1 0 1 1 1 1 7. Construct a circuit to generate the following wave.
1 0 1
Model Waveforms Astable multivibrator Symmetry waves
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Electronic Circuit Lab Manual
Asymmetr y waves
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Electronic Circuit Lab Manual
Monostable multivibrator:
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Electronic Circuit Lab Manual
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Electronic Circuit Lab Manual
Bistable multivibrator:
OBSERVATIONS: Astable Multivibrator Design parameter and components used: i)
Symmetry wave:
Given that
ii)Asymmetry wave: Given that Choose Department of ECE, VKCET
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Electronic Circuit Lab Manual
Monostable Multivibrator Design parameter and components used: Given that period of trigger signal Ti=2ms
and time
Bistable Multivibrator Given that
Wave forms: i)
Astable multivibrator (Symmetry)
ii)
Astable multivbrator (Asymmetry)
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Electronic Circuit Lab Manual iii)
Monostable multivibrator
Viva Questions: 1. Maximum frequency of oscillation of astable multivibrator is limited due to which property? 2. Give the applications of multivibrators. 3. Give the expression for the delay in trailing edge of square wave generated by astable multivibrator. 4. Define duty cycle. 5. Compare three multivibrator circuits. 6. Which circuit is referred as one-shot circuit and why? 7. Which multivibrator operates as SR flip-flop and why? 8. Which multivibrator is called free running multivibrator and why? 9. Triggering a monostable multivibrator during TON , what will happen to the
output?
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Electronic Circuit Lab Manual Expt. No. 8
OSCILLATORS Objectives: Oscillators.
a) To study the operation of Phase shift, Wien bridge, Hartley and Colpitts b) To simulate oscillator circuits using PSPICE
Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. Capacitors. 7. Inductors. 8. Inductance decade box 9. Capacitance decade box 10. SL100 BJTs / BEL100N/BC107 11. Connection Wires. 12. Oscilloscope Probes. Circuit diagram: 1. RC phase shift oscillator:
Fig.1
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Electronic Circuit Lab Manual 2. Wien Bridge Oscillator:
Fig. 2(a)
Fig. 2(b)
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Electronic Circuit Lab Manual 3. Hartley Oscillator:
Fig. 3 4. Colpitts Oscillator:
Fig. 4 Department of ECE, VKCET
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Electronic Circuit Lab Manual Theory: Oscillators are circuits that produce a repetitive waveform with only a DC voltage at the output. The output waveform can be sinusoidal, rectangular, triangular, etc. At the base of almost any oscillator there is an amplification stage with a positive (regenerative ) circuit that will produce a phase shift and attenuation. Positive consists in the redirecting of the output signal to the input stage of the amplifier without a phase shift. This signal is then amplified again generating the output signal, which produces the signal. This phenomenon, in which the output signal “takes care” of itself in order to generate continuum signal is called oscillation. Two conditions then should be fulfilled to have a stable oscillator: 1. The phase shift of the loop should be 0 2. The overall gain of the loop should be 1 In order to arrive to the stable operation of the oscillator, during the starting period the gain of the loop should be greater than one, to allow the amplitude of the output signal to achieve the desired level. These conditions are called Barkhausen criteria. Sinusoidal oscillators are classified into two types: i) RC oscillators ii) LC oscillators RC oscillators use RC elements in the branch. They are useful to frequencies up to 200kHz. Two types of RC oscillators are: i) RC phase shift oscillator ii) Wien Bridge oscillator Figure 1 shows RC phase shift oscillator, which uses RC coupled amplifier as inverting amplifier and three RC networks as circuit with voltage shunt . Each RC circuit provide at least 60o phase shift, so total 180o phase shit. The gain of the network is
The frequency of oscillation is
and the current gain of the amplifier to satisfies the Barkhausen criteria is . Figure 2 shows Wien Bridge oscillator. It consists two stage RC coupled amplifier as non-inverting amplifier (360o phase shift) with voltage series negative and voltage shunt positive . Wien Bridge contains series RC and parallel RC network, while resistor element act as resistance arms of the bridge. Resistor arms provide voltage series and RC resonance arms provide voltage shunt . The bridge offer 360o phase shift at resonance frequency and the gain introduced by the network is . So the gain of the amplifier , to satisfy Barkhausen criteria. The frequency of oscillation is
. The main advantage of
this oscillator over Phase shift oscillator is its amplitude stability due to the negative . Department of ECE, VKCET
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Electronic Circuit Lab Manual LC oscillator uses amplifier with 180o phase shift and LC tuned circuit as network. These oscillators are suitable for high frequency oscillation because of it phase stability, frequency stability and less harmonics. The two familiar LC oscillators are: i) Hartley Oscillator ii) Colpitts Oscillator Figure 3 shows Hartley Oscillator circuit and it consists of a parallel LC resonator tank circuit and RC coupled amplifier. It uses a pair of tapped coils and a capacitor to produce regenerative . The output voltage is developed across and the voltage is developed across . The attenuation caused by the network
. So the gain of the amplifier,
. The tank circuit determines the
operating frequency of the Hartley oscillator and is where
,
.
Figure 4 shows Colpitts Oscillator circuit and it consists of a parallel LC resonator tank circuit and RC coupled amplifier. It uses a pair of tapped capacitors and an inductor to produce regenerative . The output voltage is developed across and the voltage is developed across . The attenuation caused by the network
. So the gain of the amplifier,
operating frequency of the oscillator and is
. The tank circuit determines the , where
. This
oscillator has better frequency stability than Hartley oscillator. Design: 1. RC Phase Shift Oscillator:
Given that For amplifier We have
(Given
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>> required
)
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Electronic Circuit Lab Manual Design for amplifier:
(or for better stability
)
(Typical value of β =100)
Design for network: Let (Designed Av > hfe)
(Use 1kΩ potentiometer to get accurate value)
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Electronic Circuit Lab Manual 2. Wien Bridge Oscillator : Given that For amplifier We have Where k ≤ 0.5
is the gain of cascade amplifier with . Then factor
Design of amplifier:
(We are using negative , so ignore the loading effect and use same design for each stage)
(Typical value of β =100)
Design of RC network for Wien Bridge:
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Electronic Circuit Lab Manual
Design for network:
Let (Use 10k pot) 3. Hartley Oscillator: Given that We have
where
And loop gain According to Barkhausen criteria Then Design for amplifier: Choose (Deg is similar to amplifier used for RC phase shift oscillator. Use low value for IC, to avoid loading effect at the input and output of the amplifier with LC tuned circuit. Low IC value provide medium matched impedances with the available L1 and L2)
Design of LC circuit: Choose L1 and L2 according to the availability and the conditions . Department of ECE, VKCET
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Electronic Circuit Lab Manual and Let L1= 10µF (Use Inductance Decade box) and L2 = 470µF (Available) Then
and is less than the gain of the amplifier
Check the conditions
at resonant frequency fo. (Where )
(If standard capacitor is not available, use Capacitance Decade box) 4. Colpitts Oscillator: Given that We have
where
And loop gain According to Barkhausen criteria Then Design for amplifier: Choose (Deg is similar to amplifier used for RC phase shift oscillator. Use low value for IC, to avoid loading effect at the input and output of the amplifier with LC tuned circuit. Low IC value provide medium matched impedances with the available C1 and C2)
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Electronic Circuit Lab Manual
Design of LC circuit: Choose C1 and C2 according to the availability and the conditions . and Let C1= 0.1µF and C2 = 0.001µF (Both are available) Check the conditions
at resonant frequency fo. (Where )
(Use Inductance Decade box) Procedure: Steps (RC phase shift oscillator) 1. Check the components 1. Connect the circuit diagram 2. Turn on the power supply 3. Connect the CRO probe to the output 4. Vary the potentiometer
to get a proper wave form
5. Observe the amplitude and frequency of output wave form
6. Change C and observe the variation in frequency of the output wave 7. Change RC and observe the variation in amplitude of the output signal
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Electronic Circuit Lab Manual 8. Connect CRO probes to the nodes of RC network and observe the 60o phase
shift signals Steps (Wien Bridge oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the potentiometer
to get a proper wave form
6. Observe the amplitude and frequency of output wave form 7. Change C and observe the variation in frequency of the output wave Steps (Hartley oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the inductance decade box to the desired value
6. Observe the amplitude and frequency of output wave form 7. Change C and observe the variation in frequency of the output wave Steps (Colpitts oscillator) 1. Check the components 2. Connect the circuit diagram 3. Turn on the power supply 4. Connect the CRO probe to the output 5. Vary the inductance decade box to the desired value 6. Observe the amplitude and frequency of output wave form Department of ECE, VKCET
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Electronic Circuit Lab Manual 7. Change L and observe the variation in frequency of the output wave
Pre-lab Assignments: 1. Design RC network of RC phase shift oscillator for frequency 20kHz. 2. Design RC network of Wien bridge oscillator for frequency 15kHz. 3. Design tuned circuit of Hartley oscillator for frequency 500kHz. 4. Design tuned circuit of Colpitts oscillator for frequency 750kHz. 5. Compare phase shift oscillators and tuned oscillators. 6. Define frequency and amplitude stabilization used in oscillators. Model Waveforms Phase Shift Oscillators
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Electronic Circuit Lab Manual Tuned Oscillators
Simulated Results: a) RC Phase Shift Oscillator
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Electronic Circuit Lab Manual b) Wien Bridge Oscillator
(Only real time simulation using virtual oscilloscope is possible. SPICE simulation is not possible !) c) Hartley Oscillator
d) Colpitts oscillator
(To simulate inductors using SPICE, connect a low resistance of value 10mΩ in series with it.)
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Electronic Circuit Lab Manual OBSERVATIONS: 1. RC Phase Shift Oscillator: Design parameters and components used: Given that For amplifier
(Use 1kΩ potentiometer to get accurate value) Wave form:
2. Wien Bridge Oscillator :
Design parameters and components used: Given that For amplifier
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Electronic Circuit Lab Manual (Use 10k pot) Wave form:
3. Hartley Oscillator:
Design parameters and components used: Given that For amplifier
L1= 10µF L2 = 470µF Wave form:
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Electronic Circuit Lab Manual 4. Colpitts Oscillator: Design parameters and components used: Given that For amplifier
C1= 0.1µF C2 = 0.001µF (Use Inductance Decade box) Wave form:
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Electronic Circuit Lab Manual Expt. No. 9 SCHMITT TRIGGER Objective: To study the operation of Schmitt trigger circuit using BJT. Components and equipments required: 1. Oscilloscope (Scope/CRO). 2. Function Generators (FG). 3. DC power supply. 4. Project Breadboard. 5. Resistors. 6. SL100 BJTs / BEL100N/BC107 7. Connection Wires. 8. Oscilloscope Probes. Circuit diagram:
Fig. 1
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Electronic Circuit Lab Manual Theory: Schmitt trigger is a threshold circuits with positive having a loop gain > 1. The circuit is named "trigger" because the output retains its value until the input changes sufficiently to trigger a change: in the non-inverting configuration, when the input is higher than a certain chosen threshold (UTP), the output is high; when the input is below a different (lower) chosen threshold (LTP), the output is low; when the input is between the two, the output retains its value. This dual threshold action is called hysteresis and implies that the Schmitt trigger possesses memory and can act as a bistable circuit (latch). There is a close relation between the two kinds of circuits that actually are the same: a Schmitt trigger can be converted into a latch and v.v., a latch can be converted into a Schmitt trigger. Design: Given that Upper threshold point voltage
Choose
(Determines voltage drop at output when Q2 is ON, so keep a low value)
Lower threshold point voltage
Choose Department of ECE, VKCET
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Electronic Circuit Lab Manual Procedure: Steps 1. Check the components 2. Connect the circuit 3. Turn on power supply, apply input signal (10Vpp, 1kHz).
4. Connect CRO channel 1 (Y) probe to output and channel 2 (X) probe to input 5. Observe input and output wave 6. Put the CRO in XY mode and observe the hysteresis 7. Observe output for different input signal by changing signal mode of function generator. 8. Turn off power supply 9. Connect variable dc source to the input 10. Turn on power supply. 11. Vary input dc voltage from 0V to 4V, note down the change in output for VUT 12. Vary input dc voltage from 4V to 0V, note down the change in output for VLT
Pre-lab Assignments: •
Consider the circuit shown in fig.1. Find the Hysteresis voltage of the circuit, if
•
For the input wave shown below, plot the output wave for the circuit in fig.1.
Where Vm=10V Department of ECE, VKCET
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Electronic Circuit Lab Manual Model Waveforms Input and Output waveforms:
Hysteresis Curve
Hysteresis Voltage VH = VUT - VLT = 2V Tabular Column a)
For UTP Vin (V) 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4
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Vo (V)
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Electronic Circuit Lab Manual b) For LTP Vin (V) Vo (V) 4 3.6 3.2 2.8 2.4 2 1.6 1.2 .8 0.4 0 (Observe the hysteresis curve on oscilloscope by applying V in as X-axis signal and Vo as Yaxis signal. Put oscilloscope in XY mode) OBSERVATIONS: Given parameters and components used: Given that
Input and output wave forms:
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