Electronic Circuit Analysis lab Viva Questions with Answers Part I

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Multistage Amplifiers:

1. What is  difference between Amplifier and Attenuator?
Both are linear systems but Amplifier's gain is more than unity (+ve dB), Attenuator gain is less than unity (-ve dB)
2.Which Amplifier will amplify voltage and current?
common emitter amplifier
3. What are the advantages over single stage amplifier?
In single stage amplifier if we try to get more gain, bandwidth will be decreased viceversa. So get more bandwidth and gain combination we generally use multistage amplifier. but multistage amp bandwidth is less than single stage.
4.what are the classifications of Multistage amplifiers?
Based on Active device used:  BJT and FET
Based on type of coupling: RC coupled, Transformer coupled and Direct coupled amplifiers.
5. What are the different BJT multistage amplifier configurations?
CE+CE, CE+CC, CE+CB, CC+CC Amplifiers
6. What are the different FET multistage amplifier configurations?
CS+CS, CS+CD, CS+CG and CD+CD Amplifiers
7. what is the ratio of transformer coil turns in transformer coupled amp?
1:1
8. Define cut off frequency?
It is the frequency at which the gain is 70.07% of it's maximum or 3dB lesser than maximum
9. what are the formulas for low and high cut off frequencies of multistage amplifiers?

 where F_l, F_h represents low and high cut off freq for multistage amp 
f_l,f_h represents low and high cut off freq for single stage amp 
10. what is the gain of multistage amp?
It is equal to square of single stage amp gain.

Feedback amplifiers:

1. What is meant by feedback, what are the different types?
Feedback is a path which establish a connection from output of a device to it's input.
It is two types: +ve feedback, -ve feedback.
2. What is -ve feedback and where it is used?
If a fraction of output is subtracted from the input then that is called as -ve feedback. it is used get a stable operation. if we implement -ve feedback then that becomes an amplifier.
3.What is +ve feedback and where it is used?
If a fraction of output is added to the input then that is called as +ve feedback. it is used get a output with out input like oscillators.
4. what are the different -ve feedback techniques in amplifiers?
Voltage- Series amplifier, Voltage - Shunt Amplifier, Current - Series Amplifier, Current - shunt amplifier.
5. what happens to the gain if we establish -ve feedback to the amplifier?
Decreased
6. what happens to the Bandwidth if we establish -ve feedback to the amplifier?
Increased.
7. compare all -ve feedback amplifiers in terms of  input and output amplifiers?
                                                Input imp     Output imp
Voltage- Series Amplifier       decreased      increased
Voltage - Shunt Amplifier      decreased      decreased
Current - Series Amplifier      increased      increased
Current - Shunt Amplifier      increased      decreased
8. what are the other names of different -ve feedback amplifiers?
Voltage- Series Amplifier   :   Series- shunt amplifier
Voltage - Shunt Amplifier   :   Shunt - Shunt amplifier
Current - Series Amplifier   :   Series - Series amplifier
Current - Shunt Amplifier   :   Shunt - Series amplifier
9. what are the different types of distortions present in amplifier?
Harmonic, frequency, phase distortions
10. self bias circuit contains which feedback?
Voltage - Series feedback 
11. collector to emitter feedback circuit contains which feedback?
Voltage - Shunt feedback.
12. what is the forward path gain and feedback gain of voltage - series feed back amplifier?
forward path gain= g₂₁, feedback path gain= h₁₂
13. what is the forward path gain and feedback gain of voltage - shunt feed back amplifier?
forward path gain= Z21, feedback path gain= Y₁₂
14. what is the forward path gain and feedback gain of current - series feed back amplifier?
forward path gain= Y21, feedback path gain= Z₁₂
15. what is the forward path gain and feedback gain of current - shunt feed back amplifier?
forward path gain= h21 , feedback path gain=  g₁₂

                                                                                                                           

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