Electronic Circuits II–Question Bank 2012 Edition

Anna University

EC2251: ELECTRONIC CIRCUITS II

SEM / YEAR: IV/ II

QUESTION BANK – 2012 Edition

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UNIT I

FEEDBACK AMPLIFIERS

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PART-A

1. Define positive and negative feedback.

2. Define loop gain.

3. List the characteristics of negative feedback amplifiers.

4. Addition of negative feedback to an amplifier reduces its voltage gain from 300 to 60.Determine the feedback factor.

5. What are the different classifications of negative feedback amplifier?

6. How negative feedback causes reduction in noise in amplifiers?

7. Draw the equivalent circuit of a transconductance amplifier.

8. Derive using a block diagram the closed loop forward transfer ratio Af of a feedback system.

9. If an amplifier has a gain of 400and feedback ratio is 0.1,find the gain with negative feedback

10. Compare the input and output resistance for a voltage and current shunt feedback amplifier.

11. Draw a block diagram of voltage shunt feedback feedback amplifier and give its input and output resistance.

12. What are the disadvantages of negative feedback?

13. How negative feedback reduces distortion in an amplifier?

14. Define feedback factor.

15. What are the advantages of negative feedback in amplifier.

16. Define desensitivity of transfer gain.

17. Determine the gain of an amplifier with feedback,when the open loop gain is 200 and the feedback factor is 0.2.

18. Determine the gain with feedback for the amplifier with the open loop and feedback factor 0.1.

19. Identify the type of feedback of the circuit shown:

PART-B

1. Draw the circuit of a current series feedback amplifier and explain . Derive expressions for input and output impedance.

How does it improve the stability of the amplifier. (16)

2. (i) Draw the block diagrams of the four possible feedback topologies and explain. (6)

(ii) Prove that the bandwidth of the amplifier increases with negative feedback. (10)

3. (i) Show how negative feedback reduces gain of an amplifier. (8)

(ii) Explain the effect of negative feedback on the input resistances for a voltage shunt feedback amplifier. (8)

4. Explain the working of voltage series feedback amplifier with circuit diagram and small signal equivalent circuit. Derive the expressions for voltage gain, input impedance and output impedance. (16)

5. (i) Draw the circuit diagram and equivalent circuit for current shunt feedback amplifier and derive the expression for total voltage gain. (10)

(ii) what are the different performance measures of feedback amplifiers? Discuss each in brief. (6)

6. (i)What is the effect of negative feedback on the bandwidth and distortion of an amplifier. (10)

(ii) A negative feedback is used to reduce the noise from an amplifier by 80%.Waht must be the percentage negative feedback to accomplish this if the amplifier voltage gain is 100? (6)

7. Draw the circuit of an emitter follower. Identify the type of negative feedback.calculate the gain, input and output resistance with and without feedback. (16)

8. Describe with necessary derivations, discuss the effects of negative feedback amplifier. (16)

9. (i) Discuss the classification of feedback amplifiers with schematic (topology).How is impedance level modified in each type? (8)

(ii) Derive expression for Avf with positive and negative feedback and state condition for stability in negative feedback amplifiers. (8)

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UNIT-II

OSCILLATORS

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PART A

1. What is oscillator?

2. What are the classifications of Oscillators?

3. What are the factors which affect the frequency stability of an oscillator?

4. Draw the equivalent circuit of a quartz crystal.

5. A wein bridge oscillator is used for operation at 10KHz . If the value of the resistance R is 100 K ohms , what is the value of C required.

6. Define Barhausen Criterion.

7. What are the types of feedback oscillators?

8. What are the conditions for oscillation?

9. Define Piezoelectric effect.

10. Draw the equivalent circuit of crystal oscillator.

11. What is Miller crystal oscillator?

12. State the frequency for RC phase shift oscillator.

13. What is Q factor?

14. What is dissipation factor?

15. Draw the electrical equivalent circuit of crystal and mention the significance of each component.

16. Draw the Miller’s oscillator circuit.

PART B

1. Describe Hartley oscillator with neat circuit diagram . Determine the frequency of oscillations and the oscillation condition for it. (16)

2. Write short notes on

(i)Milter oscillator (8)

(ii) Crystal oscillator (8)

3. (i)Sketch the circuit and explain the operation of a RC phase shift oscillator .Derive the expression for frequency and condition for sustained oscillations for the circuit. (12)

(ii)Explain the need for three RC networks for the circuit functioning. (4)

4. With a neat circuit diagram ,explain the operation of a transistor pierce crystal oscillator. (16)

5. Explain the principle of operation of a wein bridge oscillator. (16)

6. Draw the amplitude and phase conditions that are to be satisfied in LC oscillators using pi network.Hence obtain the frequency of oscillator of a Hartley oscillator. (16)

7. (i)With circuit diagram drive an expression for frequency of oscillation of a Clapp oscillator .Explain how Barhausen conditions are satisfied. (8)

(ii) Bring out the advantages of Clapp oscillator over Colpitt oscillator. (8)

1. What are the advantages of tuned amplifiers?

2. What are the disadvantages of tuned amplifiers?

3. What is neutralization?

4. What are double tuned amplifiers?

5. What is a stagger tuned amplifier?

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UNIT III

TUNED AMPLIFIERS

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PART A

6. What are the advantages of double tuned over single tuned?

7. What are the different types of neutralization?

8. What is rice neutralization?

9. What is unloaded Q?

10. What are the different coil losses?

11. A tuned amplifier is designed to receive A.M. broad cast of speech signal at 650kHz. What is needed Q for amplifier?

12. Why neutralization is used in tuned amplifiers?

PART B

1. (i)Explain the effect of changing Q of the coil used in tank circuit on its bandwidth. (8)

(ii) Derive the equation for 3 dB bandwidth of capacitance coupled single tuned amplifier. (8)

2. (i)What is stagger tuned amplifier? Explain its working. (8)

(ii)Write brief notes on Hazeltine neutralization.

3. Define Quality factor.Obtain the quality factor for a parallel resonant circuit. (16)

4. (i)Explain the working and frequency response of a single tuned amplifier circuit. (12)

(ii)What are synchronous and stagger tuned amplifier circuits. (4)

5. With circuit diagram and waveforms explain the operation of a Schmitt trigger circuit using two transistors for a sinusoidal input. (16)

6. (i)Draw a class c tuned amplifier and drive its efficiency. (8)

(ii)Describe any one method of neutralization used in tuned amplifier. (8)

7. (i)Draw the single tuned amplifier and explain the frequency response. (6)

(ii)Drive the expression for its gain and cutoff frequency (6)

(iii)What is meant by synchronous tuning of tuned amplifier. (4)

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UNIT-IV

WAVE SHAPING AND MULTIVIBRATOR CIRCUITS

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PART A

1. What is multivibrator?

2. Name the types of Multivibrators?

3. How many stable states do bistable Multivibrator have?

4. What are the applications of bistable Multivibrator?

5. What are the different names of bistable Multivibrator?

6. Why is monostable Multivibrator called gatting circuit?

7. Why is monostable Multivibrator called delay circuit?

8. What is the main characteristics of Astable Multivibrator?

9. What is the other name of Astable Multivibrator- why is it called so?

10. What are the two types of transister bistable Multivibrator?

11. How are the values R1, R2 and VBB chosen in bistable Multivibrator?

12. What is self biased Multivibrator?

13. What are the other names of speed up capacitors?

14. Define transition time.

15. Define resolving time.

16. Define gate width.

17. What are the advantages of monostable Multivibrator?

18. What are the applications of astable Multivibtrator?

19. What is a complementary Multivibrator?

20. What is the important application of Schmitt trigger?

PART B

1. (i)Explain the working principle of complementary collector coupled astable multivibrator. (8)

(ii)With neat circuit diagram, explain the operation of bistable multivibrator. (8)

2. (i)Describe the different triggering methods used for multivibrator circuits. (8)

(ii)Draw and explain Schmitt trigger circuit and also draw the its waveform. (8)

3. (i)Draw the circuit of a collector coupled transistor monostable multivibrator.Sketch the waveforms at base and collector for each transistor when the circuit is trigerred and explain its working. (10)

(ii)Explain circuits used to trigger a transistor monostable multivibrator circuit. (6)

4. Design a Schmitt trigger circuit for Vcc=10 V;UTP=5 V;LTP=3V.Assume hfe=100 and Ic=1 mA. (16)

5. Design a monostable multivibrator for the following specifications:Vcc=10 V;Vbb=6V;Ic=1 mA;duration of output pulse=14 sec;hfe min=100;Icbo=0;Vbe=-0.5 V. (16)

6. (i)Explain the working of emitter coupled astable multivibrator with a circuit diagram and derive for its frequency. (8)

(ii)Design the collector coupled astable multivibrator using Vcc=20V and Ic sat= 3 mA to generate a pulse wave at f=2 kHz with 70% duty cycle. (8)

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UNIT V

BLOCKING OSCILLATORS AND TIMEBASE GENERATORS

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PART A

1. Define Blocking Oscillator.

2. What are the two important elements of Blocking Oscillator?

3. What are the applications of blocking Oscillator?

4. Give the expression for co-efficient of coupling.

5. Give the formula for transformation ratio.

6. Define rise time.

7. Define overshoot.

8. Define flat top response.

9. Define droop or a tilt.

10. What are the applications of pulse transformer.

11. When do the core saturates?

12. What are the two types of astable Blocking Oscillator?

13. Define Sweeptime in sawtooth generator.

14. Define Displacement error in the sawtooth generator.

15. What is constant current charging?

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PART B

1. (i)Explain how blocking oscillator can be used to generate high current pulses of short duration. (8).

(ii)Explain the applications of voltage and current time base circuits. (8)

2. (i)Give the circuit diagram of milter saw tooth generator and explain its working with necessary waveforms. (8) (ii)Write brief notes on monostable blocking oscillator.

3. With a neat diagram explain the circuit for generating sweep using UJT.Obtain the expressions for sweep period and frequency. (16)

4. Explain the operation of a bootstrap ramp generator circuit.Discuss the advantages of this circuit with other ramp generators. (16)

5. (i)With circuit diagram explain the operation of a linear voltage time base generator. (8)

6.	(i)Explain the working of a free running blocking oscillator. (ii)How a high pass RC circuit is used as a differentiator?	(8) (8)
	(ii)Obtain the period of oscillation of a UJT relaxation oscillator.	(8)
7.	Explain bootstrap saw-tooth generator with circuit diagram and draw the output signal.	(16)
8.	(i)Describe Monostable blocking oscillator using base timing.	(8)
	(ii)Explain UJT sawtooth generator in detail.	(8)

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