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Dept of Electronics and Communication Engineering ECA Lab

Vishnu Sree Institute of Technology Page 1

1. COMMON EMMITER AMPLIFIER

OBJECTIVE:

1. To simulate the common emitter amplifier using P-spice software and study thetransient and frequency response.

2. To determine the phase relationship between the input and output voltages byperforming the transient analysis.3. To determine the maximum gain, 3db gain, lower and upper cut off frequencies andbandwidth of CE amplifier by performing AC analysis.

SOFTWARE TOOL:

P- Spice/ Multisim- 10 /

THEORY:

The practical circuit of CE amplifier is shown in the figure. It consists of different circuitcomponents. The function of these components is as follows:

(i)Biasing Circuit:The resistances R1, R2 and RE form the voltage divider biasing circuit for the CEamplifier. It sets the proper operating point for the CE amplifier.

(ii)Input Capacitor C1:The capacitor couples the signal to the transistor. It blocks any DC component present inthe signal and passes, only AC signal for amplification. Because of this, biasingconditions are maintained constant.

(iii)Emitter Bypass Capacitor CE:

An emitter bypass capacitor is connected in parallel with the emitter resistance RE,to provide a low resistance path to amplified AC signal. If it is not inserted, theamplified AC signal passing through RE will cause a voltage drop across it. This willreduce output voltage, reducing the gain of CE amplifier.

(iv) Coupling Capacitor C2:The coupling capacitor couples the output of the amplifier to the load or to the nextstage amplifier circuit. It blocks DC and passes only AC part of the amplified signal.

OPERATION:

When positive half cycle of the signal is applied the voltage between base and emitter

(VBE) is increased because it is already positive with respect to ground. So forward bias isincreased i.e., the base current is increased. Due to transistor action the collector currentIC is increased times. When this current flows through RC, the drop across RC is ICRCincreases considerably. As a consequence of this, the voltage between collector andemitter (VCE) decreases. In this way, amplified voltage appears across RC. Therefore thepositive going input signal appears as negative going output signal i.e., there is a phaseshift of 180 between input and output.

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PROCEDURE:

1. SCHEMATIC -

1. Select the components form the symbol library and place it on Schematic window.2. The selected symbol is displayed on the screen in red. Move the symbol to the desired

location using the mouse.3. User can change the view of most symbols by performing the following operations:

rotate, mirrors and flip.4. Wires and junctions are used to wire together parts and indicate electrical connection.5. To draw a wire, select the wire menu command, move the cursor to the wire starting

position and click the left mouse button or press enter. Now you can move the other endof wire to the desired location.

6. The junction symbol (a large dot) indicates an electrical connection between wires orbetween a wire and a part pin.

7. Most parts (components) require to specify following set of attributes by user: reference

name, value or model name and optional parameters.8. User can also change the attributes by double-clicking on a part on the schematic.9. Once circuit designing completes, the circuit has to be analyzed.10. To simulate a circuit, select the Analysis/Run Simulation from menu list of Schematic

option.11. If there are any errors during the simulation the simulator writes any applicable error

messages to the simulation output files.12. Basically three different circuit analyses can be performed: DC, AC (Frequency

Response) and Transient response.

13. Before simulation, user has to do analysis setup.14. Once analysis set is over, then perform Run simulation.15. From the analysis, plot the desired graphs, note the readings from the pots and do

calculation if any.

2. CIRCUIT FILE

1. The spice circuit file (default file name with extension .cir) is the input file for thesimulator program.

2. This is a text file, which contains the circuit netlist, simulation command and device

model statement.3. Write the circuit file for the given schematic assuming the node numbers. Save the circuit

file.4. To simulate the circuit file, select the analysis/Run simulation from the menu list of

circuit file option.5. If there are any errors during the simulation, the simulator writes any applicable error

messages to simulation output file.

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6. Basically three different circuit analyses can be performed: DC, AC (FrequencyResponse) and Transient response.


calculation if any.

CIRCUIT DIAGRAM:

CIRCUIT FILE:

Rs 1 2 500R1 3 4 47KR2 0 3 5KRc 5 4 10KRe 0 6 2K

RL 0 7 10KC1 2 8 1uCe 0 6 10uFC2 5 7 1uFVs 1 0 AC 10m SIN 0 10m 1KVcc 4 0 12VQ1 5 8 6 2n2222

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EXPECTED GRAPH:

INFERENCE:

1. From the transient analysis the phase relationship between input and output is found tobe _________ and the output amplitude is __________ for and input of ________.

2. From AC analysis the following observations are made:

Maximum Gain (absolute) :

Maximum Gain (dB) :3dB gain :Lower cut off frequency (fL or f1) :Upper cut off frequency (fH or f2) :Bandwidth (f2 f1) :

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2. COMMON SOURCE AMPLIFIER

OBJECTIVE:

1. To simulate the common emitter amplifier using P-spice software and study thetransient and frequency response.2. To determine the phase relationship between the input and output voltages byperforming the transient analysis.3. To determine the maximum gain, 3db gain, lower and upper cut off frequencies andbandwidth of CE amplifier by performing AC analysis.

SOFTWARE TOOL:

Top Spice/Multisim/Microsim/P-Spice student version

THEORY:The practical circuit for common source amplifier which uses self biasing is shown in

figure. The resistors RG, RD and RS provide stable operating point over a wide range oftemperatures and transfer characteristics. The capacitors C1, C2 blocks the dc components present in signal. Capacitor CS connected in parallel with source resistor RS provides lowresistance path such that output gain is increased. The operating point for the FET should be sochosen that it lies in pinch-off region, to act FET as an amplifier.

PROCEDURE:1. SCHEMATIC -




position and click the left mouse button or press enter. Now you can move the other end

of wire to the desired location.6. The junction symbol (a large dot) indicates an electrical connection between wires or

between a wire and a part pin.7. Most parts (components) require to specify following set of attributes by user: reference

name, value or model name and optional parameters.8. User can also change the attributes by double-clicking on a part on the schematic.9. Once circuit designing completes, the circuit has to be analyzed.

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10. To simulate a circuit, select the Analysis/Run Simulation from menu list of Schematicoption.

11. If there are any errors during the simulation the simulator writes any applicable errormessages to the simulation output files.



calculation if any.

2. CIRCUIT FILE


2. This is a text file, which contains the circuit netlist, simulation command and devicemodel statement.

3. Write the circuit file for the given schematic assuming the node numbers. Save the circuitfile.

4. To simulate the circuit file, select the analysis/Run simulation from the menu list ofcircuit file option.

5. If there are any errors during the simulation, the simulator writes any applicable error

messages to simulation output file.6. Basically three different circuit analyses can be performed: DC, AC (Frequency

Response) and Transient response.7. Before simulation, user has to do analysis setup.8. Once analysis set is over, then perform Run simulation.9. From the analysis, plot the desired graphs, note the readings from the pots and do

calculation if any.

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CIRCUIT DIAGRAM:

CIRCUIT FILE:

EXPECTED GRAPH:

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INFERENCE:



Maximum Gain (absolute) :Maximum Gain (dB) :3dB gain :Lower cut off frequency (fL or f1) :Upper cut off frequency (fH or f2) :Bandwidth (f2 f1) :

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3. TWO STAGE RC COUPLED AMPLIFIER

OBJECTIVE:

1. To simulate Two stage RC coupled amplifier using P-spice software and study thetransient and frequency response.2. To determine the phase relationship between the input and output voltages byperforming the transient analysis.3. To determine the maximum gain, 3db gain, lower and upper cut off frequencies andbandwidth of Two stage RC coupled amplifier by performing AC analysis.

SOFTWARE TOOL:


THEORY:The practical circuit of Two stage RC coupled amplifier is shown in the figure. It consists

of different circuit components. The function of these components is as follows:(i)Biasing Circuit:

The resistances R1, R2, RE1, R3, R4 and RE2 form the voltage divider biasing circuit foramplifier. It sets the proper operating point for the amplifier.

(ii)Input Capacitor C1:The capacitor couples the signal to the transistor. It blocks any DC component present inthe signal and passes, only AC signal for amplification. Because of this, biasingconditions are maintained constant.

(iii)Emitter Bypass Capacitor CE:An emitter bypass capacitor is connected in parallel with the emitter resistance RE,to provide a low resistance path to amplified AC signal. If it is not inserted, theamplified AC signal passing through RE will cause a voltage drop across it. This willreduce output voltage, reducing the gain of CE amplifier.

(iv) Coupling Capacitor C2 and C3:The coupling capacitor couples the output of the amplifier to the load or to the nextstage amplifier circuit. Here, in this circuit C2 couples the output of 1st stage to 2nd stagewhereas C3 couples the signal to load. Both blocks DC and passes only AC part of the

amplified signal.

OPERATION:

When positive half cycle of the signal is applied the voltage between base and emitter(VBE1) is increased because it is already positive with respect to ground. So forward biasis increased i.e., the base current is increased. Due to transistor action the collectorcurrent IC1 is increased times. When this current flows through RC1, the drop across RC1

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is IC1RC1 increases considerably. As a consequence of this, the voltage between collectorand emitter (VCE1) decreases. In this way, amplified voltage appears across RC1.Therefore the positive going input signal appears as negative going output signal i.e.,there is a phase shift of 180 between input and output of 1st stage. The same processoccurs at the second stage and at the output of second stage is an amplified signal which

is in phase with the input signal applied, i.e., phase shift of 360 between input and 2ndstage output.

PROCEDURE:1. SCHEMATIC -






7. Most parts (components) require to specify following set of attributes by user: referencename, value or model name and optional parameters.

8. User can also change the attributes by double-clicking on a part on the schematic.9. Once circuit designing completes, the circuit has to be analyzed.10. To simulate a circuit, select the Analysis/Run Simulation from menu list of Schematic



Response) and Transient response.13. Before simulation, user has to do analysis setup.14. Once analysis set is over, then perform Run simulation.

15. From the analysis, plot the desired graphs, note the readings from the pots and docalculation if any.

2. CIRCUIT FILE1. The spice circuit file (default file name with extension .cir) is the input file for the

simulator program.

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4. To simulate the circuit file, select the analysis/Run simulation from the menu list of




calculation if any.

CIRCUIT DIAGRAM:

CIRCUIT FILE:

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EXPECTED GRAPH:

INFERENCE:



Maximum Gain (absolute) :Maximum Gain (dB) :3dB gain :Lower cut off frequency (fL or f1) :Upper cut off frequency (fH or f2) :Bandwidth (f2 f1) :

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4. CURRENT SHUNT AND VOLTAGE SERIES FEEDBACK AMPLIFIER

AIM:

1. To simulate the current shunt feedback amplifier using P-spice software and study thetransient and frequency response.2. To determine the maximum gain, 3db gain, lower and upper cut off frequencies andbandwidth of amplifier by performing AC analysis.3. To determine the effect of feedback on gain and bandwidth.

SOFTWARE TOOL:


THEORY:

The circuit of current shunt feedback amplifier is shown in figure. In this the outputcurrent Io is fed back to the input, as a current in parallel with the input current Ii with a feedbackfactor = If/Io. This amplifier is also known as Current Amplifier. If there is no feedback thegain of the amplifier is A = IO/II. The output signal obtained is 360 phase shifted with input.

PROCEDURE:

1. SCHEMATIC -







8. User can also change the attributes by double-clicking on a part on the schematic.

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9. Once circuit designing completes, the circuit has to be analyzed.10. To simulate a circuit, select the Analysis/Run Simulation from menu list of Schematic


messages to the simulation output files.



calculation if any.

2. CIRCUIT FILE

1. The spice circuit file (default file name with extension .cir) is the input file for thesimulator program.2. This is a text file, which contains the circuit netlist, simulation command and device

model statement.3. Write the circuit file for the given schematic assuming the node numbers. Save the circuit

file.4. To simulate the circuit file, select the analysis/Run simulation from the menu list of


messages to simulation output file.



calculation if any.

CIRCUIT FILE:

CIRCUIT DIAGRAM:

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7. RC PHASE SHIFT OSCILLATOR USING TRANSISTORS

OBJECTIVE:

1. To simulate RC phase shift oscillator using P-spice software and study the transientresponse.2. To determine the frequency of oscillations and compare its value with theoreticalvalue.

SOFTWARE TOOL:


THEORY:

The circuit of RC phase shift oscillator is shown. It consist of a CE amplifier stage

followed by cascaded arrangement of capacitors and resistors. The output of last RC combinationis fed back to the base of transistor. If the loading of phase shift network is neglected; theamplifier will provide a 180 phase shift to any voltage appearing at the basr and the RC networkshifts the phase by an additional amount which s precisely equal to 180 i.e. the total phase shiftbetween input and output is 0, thereby satisfying Barkhausen criteria.

The phase shift ; given by each RC section is =. If R is made zero,then phase shift becomes 90. But making R=0 is impractical because if R=0, then voltage acrossit will become zero. Therefore in practice the value of R is adjusted such that =60. If the valueof R and C ar chosen such that, for given frequency frthe phase shift of each section is 60. Thussuch a RC ladder network produces a total phase shift of 180 between its input and output

voltages for given frequency.

PROCEDURE:

1. SCHEMATIC -






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8. User can also change the attributes by double-clicking on a part on the schematic.9. Once circuit designing completes, the circuit has to be analyzed.10. To simulate a circuit, select the Analysis/Run Simulation from menu list of Schematic




calculation if any.

2. CIRCUIT FILE




4. To simulate the circuit file, select the analysis/Run simulation from the menu list of




calculation if any.

CIRCUIT FILE:

CIRCUIT DIAGRAM:

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EXPECTED GRAPH:

INFERENCE:

Theoritical value:f = 1/ (2RC (6+4K), where K = Rc/R

Practicle value:

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9. CLASS B COMPLIMENTARY SYMMETRY POWER AMPLIFIER

OBJECTIVE:

To simulate Class B Complimentary Symmetry power amplifier using P-spice softwareand calculate its efficiency.

SOFTWARE TOOL:


THEORY:

Power amplifiers are built using different circuit configurations with the sole purpose ofdelivering maximum undistorted power to a load. The drawback of class-A amplifier that itsefficiency is low and the limitation of class-B in push pull arrangement is use of two transformer(limits frequency response) and distortion in output, are overcome by complimentary symmetry

amplifier.The practical circuit of Class-B complimentary circuit is shown in figure. Each one of thetransistors acts as emitter follower, with emitters connected together. They are biased to cutoff.During the positive half cycle, the npn transistor conducts and pnp transistor is cutoff. Duringnegative half, the pnp transistor conducts. Therefore when the output is tapped through RL we geta complete amplified waveform of the input signal. The two transistors compliments each otherand the circuit is symmetrical; hence the name complimentary-symmetry amplifier. Theamplifier may be operated under class A or class B conditions.

PROCEDURE:

1. Drag and drop the require component models from the library of spice tool.2. Connect the components as per the circuit diagram.3. Assign the values to the components.4. Apply 3V and 10 KHz sinusoidal ac input signal.5. Perform the transient analysis by making setup of step time as 0seconds and stop time as

1millisecond.6. Calculate efficiency of the amplifier.7. By varying input voltage as 5V, 10V repeat 5th and 6th steps.

CIRCUIT FILE:

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CIRCUIT DIAGRAM:

EXPECTED GRAPH:

CALCULATIONS:

When AC input voltage VIN = 1V, Vcc = 23V

Input dc power =

Irms = Iac/

Output power Pac = (Vac*Iac)/2

Efficiency = Pac/Pdc *100

INFERENCE:

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The overall efficiency of class-B complimentary symmetry power amplifier is calculatedas ___________.It is observed that as input voltage is increased the crossover distortion is reduced.

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