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Electronic Circuit Analysis & Design

Academic Year -2010

(SEMIV)

QUESTION BANK

Prepared by

Poorva Waingankar

Sandhya Save

CHAPTER 1

FREQUENCY RESPONSE OF AMPLIFIERS

Short Questions

1. What is RC coupled amplifier

2. Which components affect low frequency response of amplifier?

3.Define Miller’s theorem.

4.Which components affect high frequency response of amplifier?

5. Define bandwidth.

6. How to improve bandwidth of amplifier?

7. Define multistage amplifier?

8. Explain Mid-band analysis of single stage CE, CB, CC amplifiers.

9. Explain Darlington connection using similar complementary

transistors and bootstrapping.

10. Define cut off frequency.

11. What do you meant by Gain Bandwidth product?

12. What is lower cut off frequency?

13. Draw the hybrid pi equivalent circuit.

14. What is upper cut off frequency?

15.Draw the general shape of frequency response of amplifiers.

16. What is the difference between high and low frequency analysis of

amplifier?

Multiple Choice Questions

1.. The control of an output signal by an input signal resulting in the output signal having some

(or all) of the characteristics of the input signal is known by which of the following terms? 1.

Multiplication 2. Magnification 3. Amplification 4. Addition

2. Which of the following statements describes the relationship of input and output signals in

an amplifier?

1. The input signal is actually changed into the output signal 2. Both the input and output

signal are unchanged; neither is affected by the other 3. The input signal is controlled by the

output signal and the output signal remains unchanged 4. The input signal remains unchanged

and the output signal is controlled by the input signal

3. Why are amplifiers used in electronic devices?

1. To provide signals of usable amplitude 2. To "pick up" broadcast signals 3. To select the

proper broadcast signal 4. To change the broadcast signal to an audio signal

4. Most amplifiers can be classified in which of the following ways?

1. Function and size 2. Power requirements and size 3. Function and frequency response 4.

Frequency response and power requirements

5. What is the purpose of an amplifier- coupling network?

1. To "block" d.c. 2. To provide gain between stages 3. To separate one stage from another

4. To transfer energy from one stage to another

6. Which of the following types of coupling is usually used to couple the output from a power

amplifier?

1. RC 2. Resistor 3. Impedance 4. Transformer

7. Which of the following types of amplifiers have both high and low frequency response

limitations?

1. RC 2. Resistor 3. Impedance 4. Transformer

8. Which of the following types of coupling is most effective at high frequencies?

1. RC 2. Resistor 3. Impedance 4. Direct

.9. For maximum current at the input to a circuit, what should the relationship of the input

impedance be to the output impedance of the previous stage?

1. Higher than 2. Lower than 3. Equal to 4. The impedance relationship is immaterial

10. What type of coupling is most useful for impedance matching?

1. RC 2. Resistor 3. Impedance 4. Transformer 1-23. What is feedback? 1. The control

of a circuit output signal by the input signal 2. The control of a circuit input signal by the

output signal 3. The coupling of a portion of the output signal to the input of the circuit 4.

The coupling of a portion of the input signal to the output of the circuit

11. What is the bandwidth of an amplifier?

1. The actual frequencies the amplifier is effective in amplifying 2. The difference between the high and low frequencies seen at the input of the amplifier 3. The width, in inches, between the half-power points on a frequency- response curve 4. The difference between the lowest and highest frequency shown on a frequency-response curve

12. What are the (a) upper and (b) lower frequency limits shown? 1. (a) 8 kHz (b) 0 Hz 2. (a) 7.5 kHz (b) 0 Hz 3. (a) 6.0 kHz (b) 2 kHz 4. (a) 5.5 kHz (b) 2.5 kHz

13. What is the bandwidth shown? 1. 1 inch 2. 8 kHz 3. 3 kHz 4. 2 kHz to 8 kHz

14. Which of the following limit(s) the frequency response of a transistor amplifier? 1. The inductance 2. The transistor 3. The capacitance 4. All of the above

15. What type of feedback is caused by interelectrode capacitance? 1. Bypassed 2. Negative 3. Positive 4. Regenerative

16. What happens to capacitive reactance as frequency decreases? 1. It increases 2. It decreases 3. It remains the same 4. It cannot be determined

17. What happens to inductive reactance as frequency increases? 1. It increases 2. It decreases 3. It remains the same 4. It cannot be determined

18 What is the major factor that limits the high frequency response of an amplifier? 1. Inductance 2. Resistance 3. Capacitance 4. Transformer reactance

19. What components can be used to increase the high-frequency response of an amplifier? 1. Diodes 2. Inductors 3. Resistors 4. Capacitors

Long Questions

1. Explain low frequency analysis of amplifiers to obtain lower cut off frequency.

2. Explain high frequency analysis of amplifiers to obtain upper cut off frequency.

3. Explain analysis of frequency response of multistage amplifier.

4. Explain amplifier rise time and lag time with relation to cut off frequency.

5. Explain high frequency analysis of FET and gain bandwidth

CHAPTER 6

FEEDBACK AND STABILITY

Short Questions

1. What do you mean by feedback.

2. Explain positive feedback.

3. Explain negative feedback.

4. Explain voltage feedback.

5. Explain current feedback.

6. Sketch and label series mixer.

7. Sketch and label shunt mixer.

8. Sketch and label series voltage feedback.

9. Sketch and label series current feedback.

10. Sketch and label shunt voltage feedback.

11. Sketch and label shunt current feedback.

12. Draw the block diagram of feedback.

13. An amplifier has a gain of 2x105 without feedback. Determine the gain if negative voltage

feedback is applied. Given: â = 0.02.







17. Draw the block diagram of concept of feedback.

18. Draw the block diagram of sampling network.

19. Explain why series voltage feedback connection is mostly used.

20. Explain the effect of negative feedback on gain.

21. Explain the effect of negative feedback on input impedance.

22. Explain the effect of negative feedback on bandwidth.

23. Explain series voltage feedback.

24. Explain series current feedback.

25. Explain shunt voltage feedback.

26. Explain shunt current feedback.

27. Explain how negative feedback in an amplifier helps in reducing the distortion.

28. Explain how negative feedback in an amplifier helps in stabilizing the gain.

29. Explain how negative feedback in an amplifier helps in increasing the input impedance.

30Explain how negative feedback in an amplifier helps in reducing the output impedance.

31.Explain how negative feedback in an amplifier helps in increasing the bandwidth.

32. When negative voltage feedback is applied to an amplifier of gain 100, the overall gain falls

to 50. Calculate the feedback factor.

33. When negative voltage feedback is applied to an amplifier of gain 1000 the overall gain falls

to 6. Calculate the feedback factor.

34.When negative voltage feedback is applied to an amplifier of gain 60 the overall gain falls to

50. Calculate the feedback factor.

35. The gain and distortion of an amplifier are 150 and 5 % respectively, without feedback. If the

stage has 10 % of its output voltage applied as negative feedback, find the distortion of the

amplifier with negative feedback.

36. The gain and distortion of an amplifier are 150 and 10 respectively, without feedback. If the

stage has 15% of its output voltage applied as negative feedback, find the distortion of the

amplifier with negative feedback.

37. Explain the concept of feedback with respect to sampling network.

38. Explain the concept of feedback with respect to feedback network.

39. Explain the concept of feedback with respect to mixer network.

40. State and explain types of feedback.

41. Explain the effect of negative feedback on non-linear distortion.

42. An amplifier has an internal gain A of 300. Its output impedance is 2KΩ. Negative feedback

with feedback factor 0.02 is introduced in the circuit. Calculate the output impedance pf the

feedback amplifier.

43. Derive an expression for voltage gain of the amplifier with positive and negative feedback.

44. Distinguish between positive and negative feedback.

45. Explain how sustained oscillations are obtained with the help of positive feedback.

46. An amplifier has an internal gain A of 200. Its output impedance is 1KΩ. Negative feedback


feedback amplifier.

47. An amplifier has an internal gain A of 300. It’s output impedance is 1KΩ. Negative feedback


feedback amplifier.

48. An amplifier has an internal gain A of 300. It’s output impedance is 1KΩ. Negative feedback


feedback amplifier.


1 Which of the following terms describe the two types of feedback?

1. Positive and negative 2. Degenerative and regenerative 3. Both 1 and 2 above 4. Bypassed and unbypassed

2. What type of feedback provide an increased amplitude output signal?

1. Positive 2. Negative 3. Bypassed 4. Unbypassed

3. Distortion caused by amplifier saturation can be reduced by using which of the following types of feedback?

1. Positive 2. Negative 3. Regenerative 4. Unbypassed

4. What type feedback is provided if the feedback signal is out of phase with the input signal?

1. Unbypassed 2. Bypassed 3. Negative 4. Positive

5. What type of feedback is provided by a capacitor connected across the emitter- resistor in a common-emitter transistor amplifier?

1. Bypassed 2. Positive 3. Negative 4. Unbypassed

Long Questions

1. Explain about the analysis of an amplifier using voltage shunt feedback.

2. Explain about the analysis of an amplifier using voltage series feedback.

3. Explain about the analysis of an amplifier using current series feedback.

4. Explain about the analysis of an amplifier using current shunt feedback.

5. Discuss the general characteristics of negative feed back.

6. Derive an expression for the input resistance of voltage series feedback topology.

7. Draw a feed back amplifier in block diagram form. Identify each block and explain its

function 8 .With a neat sketch, describe the concept of feedback in amplifier.

9. Using the block diagram approach, derive an expression for

i) Input impedence of voltage series feedback amplifier

ii) Output impedence of current shunt feedback amplifier

10.Derive an expression for the input resistance of

1.Current series feedback amplifier

2.Voltage shunt feedback amplifier

11.Show by a mathematical derivation that band width of an amplifier increases with negative

feed back.

12.The H-parameter model of a transistor can be considered to represent a feedback amplifier,

due to the presence h re source using feedback formula ,find the resistance with feedback Rif.

13. .Discuss the general characteristics of negative feed back.

14.Derive an expression for the input resistance of voltage series feedback topology.

15.Draw a feed back amplifier in block diagram form. Identify each block and explain its

function

16.Using the block diagram approach, derive an expression for

i) Input impedence of voltage series feed back amplifier

ii) Output impedence of current shunt feedback amplifier

17.Derive an expression for the input resistance of

iii) Current series feed back amplifier

iv) Voltage shunt feed back amplifier

18.Show by a mathematical derivation that band width of an amplifier increases with

negative feed back.

CHAPTER 3

POWER AMPLIFIERS

Short Questions

1. Write types of amplifier based on biasing condition?

2. What is class A,B and C amplifier?

3. What is regulated power supply?

4. What are the benefits of series voltage regulator?

5. How monolithic linear regulators are fabricated?

6. What are the types of IC voltage regulator?

7. What is conversion efficiency?

8. Calculate the effective resistance R’L seen looking into the primary of a 10:1transformer

connected to an output load of 16_.

9. Calculate the transformer turns ratio required to match a 8 Ω speaker load to an amplifier

so that the effective load resistance is 7.2 k Ω.

10. What are the advantages of class B amplifier compared with class A amplifier?

11. What are the advantages of push- pull amplifier?

12. What is Harmonic distortion?

13. What is intermodulation frequency?

14. What is frequency distortion?

15. What is phase or delay distortion?

16. What is cross over distortion?

17. What are the advantages of complementary symmetry push pull amplifier?

18. What are the advantages of complementary symmetry push pull amplifier?

19. We are to match a 16 Ω speaker load to an amplifier so that the effective load resistance

is 10KΩ. What should be the transformer turn ratio?

20. We are to match a 24 Ω speaker load to an amplifier so that the effective load resistance

is 12KΩ. What should be the transformer turn ratio?


1. The signal from a radio antenna should be amplified by which of the following types of amplifier?

1. An rf voltage amplifier 2. A video power amplifier 3. A direct-current audio amplifier 4. An alternating-current power amplifier

2. The class of operation of an amplifier is determined by which of the following factors?

1. The gain of the stage 2. The efficiency of the amplifier 3. The amount of time (in relation to the input signal) that current flows in the output circuit 4. The amount of current (in relation to the input-signal current) that flows in the output circuit

3. Which of the following is NOT a class of operation for an amplifier?

1. A 2. C 3. AB 4. AC

4. If the output of a circuit should be a representation of less than one-half of the input signal, what class of operation should be used?

1. A 2. C 3. AB 4. AC

5. What class of operation is the most efficient?

1. A 2. C 3. AB 4. AC

6. What class of operation has the highest fidelity?

1. A 2. C 3. AB 4. AC

Long Questions

1. Discuss how rectification may take place in a power amplifier.

2. Draw the circuit diagram of a push pull amplifier and Explain its operation.

3. Show that even harmonics are present in the output of a push pull amplifier.

4. Draw the circuit diagram and Explain the operation with relevant waveforms of a class B

push pull amplifier. Also show that the maximum conversion efficiency of the class B

push pull amplifier is 78.5 %.

5. Derive an expression fot the maximum conversion efficiency of a class B push pull

amplifier.

6. Explain the working of series fed directly coupled class A amplifier with the help of neat

diagram and also prove that maximum efficiency is 25%.

7. Explain with neat diagram the working of a transformer coupled class A power

amplifier? Prove that the maximum efficiency is 50%.

8. Why harmonic distortion is less in Class A amplifier/

9. Explain higher order harmonic distortion.

10. . Explain RC coupled and transformer coupled power amplifier

11. Explain the classification of power amplifiers?

12. Explain complementary symmetry and push pull power amplifier.

13. How to eliminate the cross over distortion?

14. Explain the heat sink design.

CHAPTER 2

OSCILLATORS

Short Questions

1. Define oscillators and give the examples

2. What are the necessary blocks of an oscillator

3. Define positive and negative feedback.

4. Draw the equivalent diagram of a Crystal oscillator.

5. Give some name of the crystals

6. Advantages of the crystal oscillator.

7. Draw the equivalent diagram of a Wien bridge oscillator.

8. Application of Wien bridge oscillator.

9. Application of Colpits bridge oscillator.

10. List out the characterisitics of all the feedback amplifiers.

11. What is meant by Resonant circuit?

12. Define phase shift.

13.Explain Bark Hausen Criteria.


1 Which of the following terms describe the two types of feedback?

1. Positive and negative 2. Degenerative and regenerative 3. Both 1 and 2 above 4. Bypassed and unbypassed

2. What type of feedback provide an increased amplitude output signal?

1. Positive 2. Negative 3. Bypassed 4. Unbypassed

3. Distortion caused by amplifier saturation can be reduced by using which of the following types of feedback?

1. Positive 2. Negative 3. Regenerative 4. Unbypassed

4. What type feedback is provided if the feedback signal is out of phase with the input signal?

1. Unbypassed 2. Bypassed 3. Negative 4. Positive

5. What type of feedback is provided by a capacitor connected across the emitter- resistor in a common-emitter transistor amplifier?

1. Bypassed 2. Positive 3. Negative 4. Unbypassed

Long Questions

1. Explain the principle of operation and derive the Expression for Frequency of Oscillation of

Wien bridge Oscillator.


Colpits Oscillator.


RC Phase shift Oscillator.


Hartley Oscillator.

CHAPTER5

MULTISTAGE AMPLIFIERS

Short Questions

1. The absolute gain of an amplifier is 30; find its decibel in gain.

2. The absolute gain of an amplifier is 40; find its decibel in gain.

3. The input power to an amplifier is 10 mw while output power is 1.5 W. Find the gain of the

amplifier.

4. The input power to an amplifier is 20 mw while output power is 2.5 W. Find the gain of the

amplifier.

5. A multistage amplifier employs 4 stages each of which has a power gain of 20. What is the

total gain of the amplifier in db?

6. A multistage amplifier employs 3 stages each of which has a power gain of 30. What is the

total gain of the amplifier in db?

7. The gain of the second amplifier in case of two-stage amplifier is low. Comment.

8. What do you understand by multistage transistor amplifier?

9. What is need to of multistage transistor amplifier?

10. Explain the term frequency response with respect to two-stage transformer-coupled

amplifier.

11. What are the advantages of frequency with respect to two-stage amplifier?

12. What are the disadvantages of frequency with respect to two-stage transformer-coupled

amplifier?

13. Explain the term gain.

14. What is the application of two stage RC coupled amplifier?

15. Draw the block diagram of multistage amplifier.

16. Why do we prefer to express the gain in db?

17. A single stage amplifier has collector load Rc=10KÙ, input resistance Rin=1KÙ and â=100.

If RL=100Ù find the voltage gain.

18. A single stage amplifier has collector load Rc=20KÙ, input resistance Rin=2KÙ and â=100.

If RL=75Ù find the voltage gain.

19. A multistage amplifier consists of three stages; the voltage gain of the stages are 60,100 and

160 calculate the overall gain.

20. With the neat diagram explain the application of two-stage transformer-coupled amplifier

21. Explain the term frequency response.

22. Explain the term decibel gain.

23. Why does transformer coupling give poor frequency response?

24. A multistage amplifier consists of four stages; the voltage gain of the stages are 60,80, 100

and160 calculate the overall gain.

Long Questions

1. Design a two stage RC coupled CS amplifier. Using BFWII to have I AV i,12, Vorme =3v,

R1 >, 1MΩ, IDS = 1mA.

2. Explain working of Cascode amplifier and analyse the same to calculate Av,Ri ,Ro.

3. Design a RC coupled two Stage CS Amplifier to meet the following requirement.

AV ≤ 100, Vorms = 3V, RI > 1M Ω if IDSQ = 1mA,

Assuming the following FET parameter rd = 50k, IVPI = 4V, gmo = 5000 µ , IDSS = 7.mA

Calculate the AV Ri and R0 for the designed circuit.

4. Design a RC coupled two stage CS amplifier to meet the following requirements:

AV ≥ 100 , Vorms = 3V, Ri ≥ 1M If IDSQ = 1 mA.

Assuming the following FET parameter r = 50 k, I VP I = 4 V, gmo = 5000µ U , IPSS = 7 mA

5.Design a two stage R.C amplifier for the following requirements:-

Small signal a.c voltage gain AV = 1600 Sico = ≤8 Lower cut- off frequency fL ≤ 15 HZ D.C.

supply voltage =15 volts. Determine VQmax, Rin, R0 and total current drawn from the supply for the

design circuit. (you may neglect hre and hoe ).

6. Design a two stage RC couple amplifier for audio frequency applications suitable for low frequencies

upto 15 Hz if I Av I≤ 1600, Rin ≤ 3Ω and output a.f. voltage required is 2.5 volts. Select the transistors

required from the data sheet given on the last page use the specifications given the rain, Detrmine the

voltage gain of each stage and Rin and Ro of the amplifier designed.

CHAPTER5

DIFFERENTIAL AMPLIFIERS

Short Questions1.Why differential amplifier is necessary?

2. Define differential amplifier.

3. Draw the neat-labeled diagram for dual input, balanced output.

4. Draw the neat-labeled diagram for dual input, unbalanced output.

5. Draw the neat-labeled diagram for single input, balanced output.

6. Draw the neat-labeled diagram for single input, unbalanced output.

7. Draw the neat-labeled diagram for emitter coupled differential amplifier.

8. Define the term CMRR.

9. CMRR for the differential amplifier should be high. Comment.

10. Define differential gain related to a differential amplifier.

11. Define common mode gain related to a differential amplifier.

12. Explain the black box concept.

13. Draw the neat-labeled diagram for dual input, balanced output.

14. Draw the neat-labeled diagram for dual input, unbalanced output.

15. Draw the neat-labeled diagram for single input, balanced output.

16. Draw the neat-labeled diagram for single input, unbalanced output.

17. Explain the necessity of constant source in differential amplifier.

18. Sketch and labeled the diagram of differential amplifier with constant current

source.

19. Sketch and labeled the graph of transfer characteristics of differential amplifier.

20. Sketch and labeled the circuit diagram of differential amplifier with constant

current source.

21. Define differential gain and common mode gain.

22. Define differential gain and CMRR.

23. Define CMRR and common mode gain.

24. Draw the transfer characteristics of differential amplifier circuits.

25. Draw the circuit diagram differential amplifier using constant current source.

Long Questions

1. Define and explain the term CMRR.

2. What are different configurations of differential amplifier? Draw the neat-labeled

diagram for dual input, balanced output and dual input, unbalanced output.


diagram for single input, balanced output and single input, unbalanced output.

4. Draw the circuit of emitter coupled differential amplifier and explain.

5. Draw the transfer characteristics of a differential and explain its significance.


diagram for single input, balanced output and single input, unbalanced output.


diagram for dual input, balanced output and single input, balanced output.


diagram for dual input, balanced output and single input, unbalanced output.

9. A differential amplifier has a differential gain Ad of 100. The input voltages

applied are íi=1mv and í2=0.9mv. Calculate the output voltage for a) CMRR=100 b)

CMRR=1000 and c) CMRR=10,000.

10. A differential amplifier has a differential gain Ad of 120. The input voltages

applied are íi=1mv and í2=0.9mv. Calculate the output voltage for a) CMRR=100 b)

CMRR=1000 and c) CMRR=10,000.

11. Define differential amplifier and explain emitter differential amplifier.

12. Define differential amplifier. Draw the transfer characteristics of a differential and

explain its significance.

13. Explain the necessity of constant source in differential amplifier. Prove that the

circuit works as constant current source.


diagram for a) dual input, balanced output, b) dual input, unbalanced output and c)

single input, balanced output.


diagram for a) dual input, balanced output, b) dual input, unbalanced output and c)

single input, unbalanced output.

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