PHY/VI/12 Student's Copy
2 0 1 8
6th Semester
PHYSICS
TWELFTH PAPER
Advanced Electronics
Revised
Full Marks 55
Time 2½ hours
PART A—OBJECTIVE
Marks 20
The figures in the margin indicate full marks for the questions
SECTION—A
Marks 5
Tick the correct answer in the brackets provided 1×5=5
1. A Wien bridge oscillator uses feedback.
only positive
only negative
both positive and negative
zero
2. Zener diode is used for
amplification
rectification
stabilization
producing oscillation in an oscillator
/497 1 Contd.
3. The phase difference between the input signal and output signal in a
common-emitter amplifier is (in radian)
p
p
2

2p
0
4. Positive feedback is used in
amplifier
oscillator
rectifier
filter
5. The gate of the JFET is biased.
reverse
forward
reverse and forward
zero
SECTION—B
Marks 15
Give very short answers to the following questions 3×5=15
1. Distinguish between n-type and p-type semiconductors on the basis of
energy band diagram.
2. Explain the working of a half-wave rectifier using p-n junction diode with a
suitable diagram.
3. What do you understand by transistor biasing and stabilization circuits?
4. Write three advantages of negative feedback.
5. Explain the UJT used as relaxation oscillator.
PHY/VI/12 2 Contd.
PART B—DESCRIPTIVE
Marks 35
The figures in the margin indicate full marks for the questions
1. State and explain Kirchhoff's current and voltage laws. 3
Explain the construction and working of Anderson bridge. 4
OR
Draw a typical current vs. voltage characteristic curve for a p-n
junction diode and explain qualitatively its main features. 4
What are load line and Q-point of a p-n junction diode? Draw the
characteristic curve showing Q-point for a basic diode circuit
containing one voltage source, a series resistance and a diode. 3
2. Explain the working of an transistor and transistor. 6
In a transistor, if I E 5 mA and I B 0 ×1 mA, what is the value of 1
OR
Explain the working principle of a full-wave rectifier with a suitable
diagram and also calculate the ripple factor of a full-wave rectifier. 7
3. What are power amplifiers? Show that in a class B push-pull amplifier
the power efficiency is 78·5%.
Draw the power diagram of transformer-coupled class A power
amplifier and locate its Q-point. 2
OR
What do you understand by hybrid parameters of a transformer? 2
Draw a hybrid equivalent circuit of—
common-emitter transistor;
common-base transistor.
Deduce an expression for voltage gain in common-emitter transistor. 5
PHY/VI/12 3 Contd.
4. With mathematical expression, show how distortion is reduced in an
amplifier with the application of negative feedback. 3
How does the negative feedback bring about change in input
impedance of an amplifier? 4
OR
With a neat diagram, explain the working of monostable multivibrator. 5
Show that the switching time (time period) of an astable multivibrator
is 1·38 times the product of R and C. 2
5. Write two advantages and disadvantages of JFET. Explain in brief the
output characteristics of JFET.
Compare MOSFET with JFET in terms of their characteristics. 3
OR
What do you mean by frequency modulation and demodulation? Using
diode detector, explain demodulation of AM wave showing the circuit. 7