Electronic Devices and Circuits (B.Tech 3rd Semester)

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NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C

1 Discuss the following:
(a) Roll of Push-Pull Amplifier.
(b) Why is the efficiency of class-C power amplifier more than class-A amplifier?
(c) Why transistor action cannot be achieved by connecting two back o back diodes?
(d) Thermal runway in transistor.
(e) Use of Photo diode and Photo transistor
(f) Use of MOSFET's
(g) Characteristics of an amplifier modified by negative feedback.
(h) properties of crystal oscillator responsible for its use in oscillators.
(i) Principal of operation of audio oscillators.
(j) Principal of operation of Regulated Power Supply.

Section-B Marks:5 Each

2. Draw the h-parameer model of a transistor and explin expression for voltage gain, current gain, input and output
impedences in terms of h-parameters.
3. Draw the circuit of a voltage divider bias circuit and explain its advantages over the fixed and collector to base
feedback bias circuits.
4. Draw the structure, symbol and V-I characteristics of p-channel JFET and MOSFET. Explain the characteristics.
5. Drive an expression for the efficiency of a class-A amplifier. Show that its maximum value is 50%.
6. Draw the circuits of vein bridge oscillator. Explin its operation and derive ite frequency of oscillations.

Section-C Marks : 10 Each

7. (a) Describe the transistor action which provides amplification.
(b) Discuss the classification of amplifiers based upon function, frequency, conduction angle, type of coupling and load.
8. Dicuss:
(a) Use of FET as VVR.
(b) Causes of distortion in amplifiers.
9. Write notes on any two of the following :
(a) C-S JFET amplifier.
(b) Tuned class-C power amplifier.
(c) R-C coupled amplifier.