ELECTRONICS CIRCUIT-1(EC2205) QUESTION BANK

ELECTRONICS CIRCUIT-1(EC2205)

MIDBAND ANALYSIS OF SMALL SIGNAL AMPLIFIERS

PART –A

1. What do you understand by Operating point? (2)
2. Why do we choose the Q point at the center of the load line? (2)
3. Name the two techniques used in the stability of the q point .explain.? (2)
4. Define stability factor &Give the expression for stability factor? (2)
5. List out the different types of biasing. (2)
6. What do you meant by thermal runway? (2)
7. Why transistor is called as a current controlled device? (2)
8. Define current amplification factor? (2)
9. What are the requirements for biasing circuits? (2)
10. When does a transistor act as a switch? (2)
11. What is biasing? (2)
12. What is an operating point? (2)
13. What is d.c load line? (2)
14. Explain about the various regions in a transistor? (2)
15. Explain about the characteristics of a transistor? (2)
16. Why the operating point is selected at the Centre of the active region? (2)
17. What is an amplifier? (2)
18. What is small signal amplifier? (2)
19. What is a Darlington pair? (2)
20. Define Common Mode Rejection Ratio. (2)
21. What is meant by Differential Amplifier? (2)
22. What do you mean by balanced and unbalanced output? (2)
23. What are the methods of improving CMRR? (2)
24. Give few applications of differential amplifier (2)
25. What are the advantages of double tuned over single tuned? (2)
26. List the four differential amplifier configurations (2)

PART –B

1. Draw the circuit of a common source FET amplifier & explain its operation? (16)
2. Briefly explain the operation of a Darlington emitter follower and also derive an
expression for its performance measures? (16)
3. What is a differential amplifier? Explain its working in common mode operation.
Obtain its AC equivalent circuit & drive the expression for voltage gain? (16)
4. Draw the circuit diagram of a differential amplifier. Explain the operation in difference
mode and common mode? (16)
5. What are the methods to improve the CMRR of differential amplifier? Detail any two
of them. (16)
6. i) What is meant by bias stability? What factors affect BJT biasing? (8)
ii)With the help of neat diagram explain the voltage divider biasing method for JFET
(8)
7. i) Explain with circuit diagram the boot strapped Darlington emitter follower. (8)
ii) Draw the circuit diagram of self-bias circuit using CE configuration and explain
how it stabilizes operating point. (8)
8. Draw the small signal hybrid model of CE amplifier and derive the expression for its
AI.AV,RI and RO. (16)

UNIT II

FREQUENCY RESPONSE OF AMPLIFIERS

PART –A
1. Draw a hybrid-π model for a BJT. (2)
2. What is the relationship between bandwidth and rise time? (2)
3. What are the high frequency effects? (2)
4. If the rise time of a BJT is 35 nano seconds, what is the bandwidth that can be
obtained using this BJT? (2)
5. Explain the usefulness of the decibel unit. (2)
6. Define the term bandwidth of an amplifier? (2)
7. State various capacitances in the hybrid model? (2)
8. Define the term bandwidth of an amplifier? (2)
9. Why it is not possible to use the h- parameters at high frequencies? (2)
10. What do you mean by the half power or 3 db frequencies? (2)

PART –B

1. Derive the expression for the CE short circuit current gain of transistor at high
frequency (16)
2. i)What is the effect of Cb’e on the input circuit of a BJT amplifier at High
frequencies? (8)
ii)Derive the equation for gm which gives the relation between gm, Ic and
temperature. (8)
3. i) Draw the high frequency hybrid –π model for a transistor in the CE
configuration and explain the significance of each component. (12)
ii) Define alpha cut off frequency. (4)
4. i) Define fα,fβ and fT and state the relation between fβ and fT (8)
ii) Explain the significance of octaves and decades. (8)
5. Define unity gain frequency. Obtain the necessary relation using transistor
frequency response. (16)
6. Using hybrid π model for CE amplifier. Derive an expression for its short circuit
current gain. (16)
7. Explain the operation of low frequency response CE amplifier. (16)

UNIT III
UNTUNED AMPLIFIERS
PART A
1. What is an effect of cascading? (2)
2. What are all the factors affecting the bandwidth of the RC
Coupled amplifier? (2)
3. Explain bypass capacitor? (2)
4. What is meant by coupling capacitor? (2)
5. Why does amplifier gain reduce? (2)
6. Explain the different regions in frequency response? (2)
7. State the types of distortions in amplifier? (2)
8. What is cross over distortion? How it can be eliminated? (2)
9. Define noise? (2)
10. Define step response? (2)
PART –B

1. Describe in detail about the different types of distortions occur in amplifier?(16)
2. i) Explain the concept of frequency response of an amplifier? (8)
ii) Classify the amplifiers? (8)
3. With the neat sketch describe the principle of operation of RC coupled amplifier?
(16)
4. Explain the operation of low frequency response CE amplifier and also discuss
the effect of bypass capacitor? (16)
5. Draw the equivalent circuit of cascaded CE stage and also derive an expression
for its performance measures? (16)

UNIT IV

FEEDBACK AMPLIFIER AND OSCILLATORS

PART –A
1. What is feed back and what are feed back amplifiers? (2)
2. What is meant by positive and negative feedback? (2)
3. What are the advantages and disadvantages of negative feed back? (2)
4. Differentiate between voltage and current feedback in amplifiers? (2)
5. Define sensitivity? (2)
6. Define De-sensitivity? (2)
7. What is the type of feedback used in an op- amp Schmitt trigger? (2)
8. Give the expression for the frequency of oscillations in an op-amp sine wave
oscillator? (2)
9. What are the conditions for sustained oscillator or what is Backhouse criterion?
(2)
10. What is Oscillator circuit? (2)
11. What are the classifications of Oscillators? (2)
12. What are the types of feedback oscillators? (2)
13. Define Piezo-electric effect? (2)
14. Draw the equivalent circuit of crystal oscillator? (2)
15. What is Miller crystal oscillator? Explain its operation? (2)
16. State the frequency for RC phase shift oscillator? (2)
17. Give the topology of current amplifier with current shunt feedback? (2)
18. What are gain margin and phase margin? (2)

19. What is the minimum value of hfe for the oscillations in transistorized RC
Phase shift oscillator? (2)
20. What is LC oscillator? (2)
21. Draw the circuit of clapp oscillator? (2)
22. How does an oscillator differ from an amplifier? (2)
23. Name two low frequency oscillators? (2)
24. Calculate the frequency of oscillation for the clapp oscillator with c1=0.1μf,
c2=1μf, c3=100pF and L=470μH (2)
PART –B
1. Discuss the differential voltage/current—series/shunt feedback connections with
expression for gain, input resistance and output resistance. (16)
2. Draw and explain various feedback amplifier topologies? (16)
3. i) explain the operation of Hartley oscillator. (10)
ii) Find the value of inductor in the Colpitts oscillator if c1=0.2μf, c2=0.02μf
And the frequency of the oscillator is 10 kHz. .Find the required gain for
Oscillator? (6)
4. Discuss in detail the characteristics of negative feedback amplifier? (16)
5. i) Give a short note on crystal oscillator? (8)
ii) Determine the voltage gain, input and output amplifier with feedback for
Voltage series feedback having A =-100, Ri=10kΩ, Ro=20 kΩ and β= -0.1 (8)
6. With a neat circuit diagram explain the working of RC phase shift oscillator.
Derive the expression for its frequency of oscillator? (16)
7. With a neat circuit diagram explain the working of Wien bridge phase shift
oscillator. Derive the expression for its frequency of oscillator? (16)
8. With the topologies compare the four types of negative feedback amplifier?(16)
9. Draw and explain the Colpitts oscillator circuit and determine the frequency of
oscillator? (16)

UNIT V

LARGE SIGNAL AMPLIFIERS

PART –A
1. What is class AB operation? (2)
2. Define conversion efficiency of a power amplifier. What is its value for class C
power amplifier? (2)
3. What is crossover distortion? How it can be eliminated? (2)
4. What is meant by Harmonic distortion? (2)
5. What is the drawback of class B amplifier? How is this minimized? (2)
6. Define thermal resistance in the context of power amplifier. (2)
7. What are the types of class B amplifier? (2)
8. Draw a quasi complimentary symmetry power amplifier? (2)
9. What is the advantage of using the output transformer for a class A amplifier? (2)
10. What is the disadvantage of transformer coupled class A amplifier? (2)

PART –B
1. i)Draw a neat circuit diagram of push-pull class-B amplifier. Explain its working.(8)
ii) For the transformer – coupled class A power amplifier circuit derive the expression
for its efficiency. (8)
2. Prove that the maximum efficiency of class B amplifier is 78.5%. and that of Class A
type is 50%. (16)
3. Draw the circuit of push pull class B power amplifier coupled using transformers and
explain the operation. Prove that all the even harmonics get eliminated. What is the
assumption made for this? (16)
4. i) Compare class A, class B and class C power amplifier in their performance and
efficiency. (10)
ii) Give the design procedure for heat sinks. (6)
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5. What is the difference between a voltage amplifier and a power amplifier? (16)
6. Discuss the advantage and disadvantage of a complementary symmetry class b
amplifier? (16)
7. With the help of neat diagram. Explain the characteristics of class A amplifier and
also derive an expression for its efficiency and figure of merit. (16)