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BSc (VI Semester) Examination
PHYSICS
Paper : PHY–363 (Old Course)
( Electronics and Communications )
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
Note : 1. Answer any five questions.
2. The figures in the margin indicate full marks for the questions.
1. (a) What do you mean by voltage source and current source? 5
(b) Explain superposition theorem. 5
(c) State and prove Thevenin’s theorem. 6
2. Describe with necessary circuit diagram :
(a) How is a p-n junction diode used as a full-wave rectifier? Find its efficiency and ripple factor. 8
(b) What is a filter circuit? Explain briefly L-section and p-section filters. 8
3. (a) What are different modes of operation of transistor? Find a relation between current gain of CE and CB transistors. 8
(b) What do you mean by transistor biasing? Why is it necessary? 5
(c) What do you mean by operating point of a transistor? 3
4. (a) Distinguish between Class A, Class B and Class C power amplifiers. 6
(b) What do you mean by harmonic distortion? Discuss Class B large signal push-pull amplifier. 10
5. (a) What is feedback in amplifier? Compare positive and negative feedbacks with their relative advantages and disadvantages. 8
(b) Discuss the working of a Wien bridge oscillator with necessary circuit diagram. Find its frequency. 8
6. (a) What are octat and hexa-decimal number systems? 4
(b) (i) Convert to octal equivalent.
(ii) Convert to binary equivalent.
(iii) Add the numbers 10011 and 110111.
(iv) Convert to hexadecimal system. 8
(c) Write a note on K-map. 4
7. (a) Why is modulation necessary in communication? Discuss the theory of frequency modulation. Compare amplitude modulation with frequency modulation. 12
(b) What do you mean by multiplexing in electronic communication? 4
8. Write short notes on any four of the following : 4×4=16
(a) R-C coupled amplifier
(b) Full adder
(c) Digital communication
(d) Zener diode as voltage regulator
(e) Z-parameter
(f) Multivibrator
