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BSc (VI Semester) Examination
PHYSICS
Paper : PHY–363 (New Course)
( Electronics and Communications )
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
1. (a) What do you mean by active and passive components of electronic circuit? 2+2=4
(b) State and explain ‘maximum power transfer theorem’. 8
(c) Write the statements of Thevenin’s and Norton’s theorems with suitable circuits. 4
2. (a) Discuss the (I-V) characteristics of a p-n junction. What is the effect of temperature on it? Discuss the mechanism of flow of current in a p-n junction under forward bias and reverse bias. 8
(b) Write the difference between ordinary p-n junction and Zener diode. Explain the terms avalanche breakdown and Zener breakdown. 6
(c) Draw the circuit diagram of a Zener diode as a voltage regulator. 2
3. (a) Describe how p-n junction is used as full-wave rectifier. Calculate its efficiency and ripple factor. 7
(b) Describe the transistor action of n-p-n transistor. 6
(c) What are different modes of operation of a transistor? Why is CE configuration widely used in amplifier? 3
4. (a) What is a DC load line and Q point of a transistor amplifier? Why is it necessary to stabilize the Q point? 9
(b) What do you mean by transistor biasing? Discuss different methods of transistor biasing. 7
5. (a) Analyze CE transistor amplifier using h parameters. Find the expressions for current gain, input resistance, voltage gain and output resistance. 10
(b) What is field-effect transistor? Draw the diagram of an n-channel FET and explain the terms source, drain, gate and channel. 6
6. (a) Distinguish between Class A, Class B and Class C amplifiers. Explain the principle and working of Class B push-pull amplifier and find out the efficiency of the amplifier. 12
(b) What is Darlington connection? 4
7. (a) State the Barkhausen criteria of oscillation. Draw the circuit diagram of phase-shift oscillator. Explain its working. 12
(b) An amplifier has voltage gain 200 without feedback. With negative feedback the gain is 20. Determine the value of b. 4
8. (a) Convert the following decimal numbers to binary numbers : 4
(i)
(ii)
(b) State and explain De Morgan’s theorem. 3
(c) Explain a full-adder circuit. 3
(d) Discuss the theory of amplitude modulation. 6
