Code No: 133AB

R16
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
B.Tech II Year I Semester Examinations, November/December - 2017
ANALOG ELECTRONICS
(Electronics and Communication Engineering)
Time: 3 Hours Max. Marks: 75

Note: This question paper contains two parts A and B.

Part A is compulsory which carries 25 marks. Answer all questions in Part A.
Part B consists of 5 Units. Answer any one full question from each unit.
Each question carries 10 marks and may have a, b, c as sub questions.

PART-A
(25 Marks)
1.a) What is Bias? What is the need for biasing? [2]
b) How does the input impedance increases due to darlington connection? [3]
c) Define Gain bandwidth product. [2]
d) Mention important characteristics of CE amplifier. [3]
e) Write the expression for basic current equation in MOSFET. [2]
f) Compare the AC circuit characteristics of the CS, CG and CD. [3]
g) List the four basic feedback topologies. [2]
h) State Barkhausen criterion for sustained oscillation. What will happen to the
oscillation if the magnitude of the loop gain is greater than unity? [3]
i) Define Harmonic distortion and intermodulation distortion. [2]
j) What are the advantages of push pull amplifiers? [3]

PART-B
(50 Marks)
2.a) In a single stage CB – amplifier circuit, RE = 20K, Rc = 10K, VEE = -20V, Vcc = 20V,
RL = 10K. Find out Ri, Ro , Ai, Av and power gain in dB.
b) Draw the circuit of two stage R-C coupled transistor amplifier and explain the
working of it. [6+4]
OR
3.a) The h-parameters of CE-amplifier are hie = 1100, hre = 2.5 × 10-4 , hfe = 50,
hoe 24 A/V and Rs = 1K, RL = 10K. Find out current and voltage gains with and
without source resistance, input and output impedances.
b) Discuss briefly Cascode amplifier. [6+4]

4. Derive the expression for the CE short circuit current gain Ai as a function of
frequency using Hybrid - π model. [10]
OR
5. Define and fT and derive the relation between and fT . [10]

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6.a) What is square law distortion? What is its effect in FET amplifiers?
b) Draw the small-signal high-frequency circuit of a common source amplifier and
derive the expression for voltage gain. [4+6]
OR
7.a) Why self-bias is not suitable for depletion type and enhancement type MOSFET?
b) In a Drain-to-gate bias circuit VCD = 12V, Rd = 2k,Rf = 10m. Calculate VGS, ID and
VDS for ID(ON) = 6mA, VGS(ON) = 8V, VGS(TH)=3V. [4+6]

8.a) Explain with the help of mathematical expressions, how the negative feedback in
amplifiers increases amplifier bandwidth and reduces distortion in amplifiers.
b) In a transistorized Hartley oscillator the two inductances are 2mH and 20μH while the
frequency is to be changed from 950KHZ to 2050KHZ. Calculate the range over
which the capacitor is to be varied. [5+5]
OR
9.a) An amplifier circuit has a gain of 60 dB and an output impedance Zo=10K. It is
required to modify its output impedance to 500 by applying negative feedback.
Calculate the value of the feedback factor. Also find the percentage change in the
overall gain, for 10% change in the gain of the internal amplifiers.
b) What are the factors that affect the frequency stability of an oscillator? How
frequency stability can be improved in oscillators. [5+5]

10.a) Derive the equation for maximum efficiency of a class A transformer coupled
amplifier.
b) Explain the principle of stagger tuning technique of transformer – coupled amplifier
that is used to obtain band pass filter characteristic with pass band of 10 KHZ with all
necessary diagrams for illustration. [5+5]
OR
11.a) Design a class B power amplifiers to deliver 25w to a load resistor RL=8ohms, using
transformer coupling. Vm=Vcc=25V. Assume necessary data.
b) Draw the circuit of double-tuned transformer-coupled amplifier. Discuss the nature of
responses of the amplifier for different values of KQ=1; KQ>1 and KQ<1. [5+5]

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