Anna University Chennai 2005 B.E Electrical and Electronics Engineering Fourth Semester - Question Paper

MODEL PAPER
B.E. DEGREE exam.
Fourth Semester
Electrical and Electronics Engineering
EC 254 — ELECTRONIC CIRCUITS
Time : 3 hours Maximum : 100 marks
ans ALL ques..
PART A — (10 ? two = 20 marks)
1. With the small signal equivalent circuit, describe the parameters of a JFET.
2. Draw the circuit diagram of a Darlington Emitter follower. elaborate the
advantages of this amplifier?
3. elaborate the advantages of using FET input stages?
4. Draw a single tuned amplifier circuit diagram and its frequency response
characteristics.
5. With a block diagram, find the closed loop transfer gain of a feedback
system.
6. Draw the circuit of a Wien Bridge Oscillator.
7. Sketch the output waveform of a Schmitt Trigger with UTP = five V and LTP =
3 V for a 12 V peak to peak one kHz sinewave input.
8. Why the RC circuit provided in fig. one is called a High Pass filter?
M 077
R
C
2 M 077
Fig. 1
9. Draw the circuit schematic of a simple three phase Half Wave Rectifier.
10. provide a functional block diagram of a switched Mode Voltage Regulators.
PART B — (5 ? 16 = 80 marks)
11. With differential mode and common mode small signal equivalent circuits,
compute CMRR for the differential amplifier with double ended output having
the subsequent specifications :
C R = one k ? , EE R = 10 k ? , ie h = one k ? , fe h = 200, h h 0 re oe ? ? .
12. (a) Using Miller’s theorem, compute V A , VS A , in R and o R of the Common
Emitter amplifier shown in fig. 2.
Fig. 2
The BJT has the subsequent parameters :
ie h = 1.1 k ?
fe h = 50
oe h
1
= 40 k ?
in R
s R
o R
o V
R?
CC ? V
C R
C C
S V
10 K
200 K
10 K
+
–
3 M 077
re h = 0.
Or
(b) (i) With a suitable circuit diagram and waveforms, discuss the
operation of a class B power amplifier using complementary symmetry
transistors. (12)
(ii) Draw the circuit diagram of a class C power amplifier. Indicate the
base and collector voltage waveforms. (4)
13. (a) (i) Derive if R and of R of a voltage series feedback amplifier. (8)
(ii) Compare the frequency response characteristics of an amplifier
with and without feedback. (4)
(iii) Draw the circuits of single stage voltage series and current series
feedback amplifiers. (4)
Or
(b) (i) Draw the circuit of a transistor Hartley Oscillator. find the
frequency of oscillation. (12)
(ii) elaborate the advantages of crystal oscillators? Draw a crystal
oscillator circuit. (4)
14. (a) Design and draw a Monostable Multivibrator for the subsequent
specifications :
CC V = 12 V; BB V = six V; C(on) I = one mA;
duration of output pulse 10 m seconds;
FEmin h = 100; I 0 CBO ? , ? BE(off) V –0.5 V.
Or
(b) (i) With circuit diagram and output voltage waveform, derive an
expression for the period of oscillation of a UJT relaxation oscillator. (10)
(ii) Sketch the output waveforms of the subsequent non linear RC wave
shaping circuits provided in fig. three and fig. 4. (6)
1 kHz
10 PP V
R
D
2 V
0 v one kHz
10 PP V
C
D
2 V
0 v
R
4 M 077
Fig. three Fig. 4
15. (a) With circuit diagram discuss the operation of a transistor series voltage
regulator with short circuit overload protection and current
preregulation.
Or
(b) (i) find an expression for the ripple factor of a capacitor input (RC)
filter that follows a full wave rectifier, using the voltage waveforms. (10)
(ii) Show that the maximum rectification efficiency R ? of a full wave
rectifier is 81%. (6)
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Earning:   Approval pending.