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### EC2251 ELECTRONIC CIRCUITS – II ANNA UNIVERSITY PREVIOUS YEAR QUESTION PAPER, IMPORTANT QUESTIONS, 2 MARKS AND 16 MARKS QUESTIONS FOR ECE DEPARTMENT

Sunday, September 25, 2011 ·

ELECTRONIC CIRCUITS – II ANNA UNIVERSITY PREVIOUS YEAR QUESTION PAPER, IMPORTANT QUESTIONS, 2 MARKS AND 16 MARKS QUESTIONS FOR ECE DEPARTMENT

SuB CODE : EC2251

ANNA UNIVERSITY PREVIOUS YEAR QUESTION PAPER,  EC2251 ELECTRONIC CIRCUITS – II IMPORTANT QUESTIONS, 2 MARKS AND 16 MARKS QUESTIONS FOR ECE DEPARTMENT

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010
Fourth Semester
Electronics and Communication Engineering
EC2251 — ELECTRONIC CIRCUITS – II
(Regulation 2008)
Time: Three hours Maximum: 100 Marks
PART A — (10 × 2 = 20 Marks)
1. What is the impact of negative feedback on noise in circuits?
2. Define sensitivity and desensitivity of gain in feedback amplifiers.
3. Mention two essential conditions for a circuit to maintain oscillations.
4. In a RC phase shift oscillator, if = = = K R R R 200 3 2 1 and
pF C C C 100 3 2 1 = = = , find the frequency of the oscillator.
5. Define tuned amplifier.
6. Define the term unloaded Q factor.
7. Give two applications of bistable multivibrator.
8. A 20 KHz, 75% duty cycle square wave is used to trigger continuously, a
monostable multivibrator with a triggered pulse duration of s µ 5 . What will be
the duty cycle of the waveform at the output of the monostable multivibrator?
9. Mention any two applications of blocking oscillator.
10. What is the function of time base circuit?
PART B — (5 × 16 = 80 Marks)
11. (a) (i) Explain how negative feedback acts on bandwidth, distortion, Input
Impedance and Output Impedance of a circuit. (8)
(ii) An amplifier has a mid-frequency gain of 100 and a bandwidth
of 200 KHz.
(1) What will be the new bandwidth and gain, if 5% negative
feedback is introduced?
(2) What should be the amount of feedback, if the bandwidth is to
be restricted to 1 MHz? (8)
Or
(b) (i) Explain voltage series and voltage shunt feedback connections. (8)
(ii) Explain Nyquist criterion to analyse the stability of feedback
amplifiers. (8)
12. (a) (i) Explain Armstrong oscillator and derive its frequency of oscillation.
(8)
(ii) A Colpitts oscillator is designed with pF C 100 1 = and
pF C 7500 2 = . The inductance is variable. Determine the range of
inductance values, if the frequency of oscillation is to vary between
950 KHz and 2050 KHz. (8)
Or
(b) (i) Explain Wien bridge oscillator and derive its frequency of
oscillation. (10)
(ii) Write a note on frequency stability of oscillators. (6)
13. (a) (i) Discuss about double tuned voltage amplifier. (8)
(ii) Discuss the effect of bandwidth on cascading single tuned
amplifiers. (8)
Or
(b) (i) Explain class ‘C’ tuned amplifier and derive its efficiency. (10)
(ii) Explain Hazeltine Neutralization Method. (6)
14. (a) (i) Sketch and define transistor switching times. (8)
(ii) What is a clipper? Explain the operation of positive and negative
diode clippers with waveforms. (8)
Or
(b) (i) Explain astable multivibrator with neat sketch of waveforms at
collector and base of transistors used in the circuit. (10)
(ii) Determine the value of capacitors to be used in an astable
multivibrator to provide a train of pulse s µ 2 wide at a repetition
rate of 100 KHz if = = k R R 20 2 1 . (6)
15. (a) (i) Explain about astable blocking oscillator with base timing. (10)
(ii) The diode controlled astable blocking oscillator has the parameters
10 = CC V V, V VB 5 . 0 = , 2 = n , = K R 5 . 1 , =10 f R , V Vr 9 = ,
mH L 3 = and pF C 100 = . Calculate the frequency of oscillation and
duty cycle. (6)
Or
(b) Write about Miller Integrator and Current-Time Base Circuit with
waveform. (16)