ANNA UNIVERSITY COIMBATORE

B.E / B.TECH. DEGREE EXAMINATIONS : MAY/JUNE 2010

REGULATION : 2008

FOURTH SEMESTER -ELECTRONICS AND COMMUNICATION ENGG.

ELECTRONIC CIRCUITS II

TIME :3Hours                                                                                                                      Max.Mark:100

PART A

(20*2=40 MARKS)

1. What are the merits of negative feedback?

2. Classify negative feedback amplifiers.

3. Define feedback factors.

4. State Nyquist stability factor.

5. Mention the essential conditions satisfied by

an oscillator circuit.

6. Draw the equivalent circuit of a quqrtz crystal.

7. Define piezo-electric effect.

8. Find the frequency oscillation of a wein bridge

oscillator with R1=R2=220kOHMS,C1=C2=250pF.

9. If the practical lower limit on C is 47pF in a Wein-Bridge

oscilltor ,what should be the fixed value of R to

produce an upper frequency limit of 200KHz?

10. Define resonant frequency?

11. Write down the expression for the bandwidth of a

tuned circiut in terms of quality factor and

resonant frequency.

12. a series resonant circuit has the following

constants:L=220mH.C=300pF,R=20ohm.Calculate resonant

frequency.

13. What is a positive clamper?

14. Draw the circuit of biased clipper with input

and output waveforms.

15. Define quality factor.

16. What are the limitations of single tuned

amplifier?

17. What do you mean by free running blocking

oscillator?

18. How is linearization achieved in current

time base circuit.

19. Mention some applications of pulse transformer.

20. What is the effect of output resistance of the

amplifier with series feedback connection and

shunt feedback connection?

PART B

(5*12 = 60 MARKS)

21.(a) Draw the block diagram of current sampling

-Series Mixing feedback configuration and

derive an expression for transfer gain,input

resistance and output resistance. (8 Marks)

(b) How the negative feedback amplifier improves

stability,reduces noise and increases the input

impedance? (4 Marks)

22. i) Identify the four possible topologies of a

feedback network.

ii) Identify the o/p signal & f/b signal for each

topology(Whether current or voltage).

iii) Identify the transfer gain & feedback factor for

each topology. (12 Marks)

23.(a) Explain RC phase shift oscillator with neat

circuit diagram. derive its frequency of

oscillation . (6 Marks)

(b) A 3 section RC Phase oscilltor has R=10KO and

C=0.01mF . (6 Marks)

(a) What is the frequency of oscillation?

(b) If the oscillator is to be made variable,

using the same values of R,what should be

the tuning range of the capacitor to

obtain a frequency range of 2KHz to 200KHz.

24.(a) Explain the working of a Colpitt's (6 Marks)

oscillator in detail and derive the frequency

of oscillation.

(b) What is crossover distortion? How it can be

eliminated ? (6 Marks)

25.(a) Derive the equation for the 'gain-bandwidth'

product of a single tuned amplifier circuit.
(6 Marks)

(b) A tank circuit has a capacitor of 100pF

and an inductor of 150mH.The series resistance

is 15ohm.Find the impedance and bandwidth

of resonant circuit. (6 Marks)

26.(a) With a neat circuit diagram, explain the working

of an Astable multivibrator. (8 marks)

(b) Describe the parallel biased clipper operation

with necessary diagrams. (4 Marks)

27.(a) With a neat circuit diagram,explain the working

of bistable moltivibrator, derive necessary

equations and plot its waveforms. (6 Marks)

(b) With neat circuit explain the operation

of a Schmitt trigger. (6 Marks)

28.(a) Draw the circuit diagram and explain the

operation of a Push-pull Astable blocking

oscillator with emitter timing. (6 Marks)

(b) Descibe briefly about UJT saw tooth generator.
(6 Marks)
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