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Engineering Electronics Question Paper
Engineering Electronics
Course:Bachelor Of Science In Manufacturing Engineering And Technology
Institution: Kenyatta University question papers
Exam Year:2009
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE ENERGY AND BACHELOR OF SCIENCE MANUFACTURING
SET 300:
ENGINEERING ELECTRONICS
DATE: Tuesday, 29th December, 2009
TIME: 2.00 p.m. – 4.00 p.m.
------------------------------------------------------------------------------------------------------------
INSTRUCTIONS:
Attempt THREE questions. Question ONE is compulsory. Marks are shown in
parenthesis at the end of each question.
Q.1
a)
Establish the following relations:-
a
i)
ß =
(3 marks)
1-a
1
ii)
? =
(3 marks)
1-a
b)
For certain transistor, IC = 5.505mA, IB = 50mAand ICO = 5mA.
Determine:
i)
Value of a, ß and I .
E
ii)
The new level of IB required to make IC equal to 10mA.
(2 marks)
c)
Draw and explain briefly the input and output characteristics of a common
emitter
transistor
connection.
(4
marks)
Page 1 of 3
d)
Draw an equivalent circuit of a thyristor (SCR) as visualized by two
transistors
(3 marks)
e)
i)
State the two draw-backs of LC oscillators.
(2 marks)
ii)
State
and
explain
the three components of transistor oscillators.
(3 marks)
iii)
Explain
the
backhausen
criterion.
(2
marks)
f)
With the aid of a diagram explain the operation of tuned collector
oscillator
(4 marks)
g)
Using Boolean technique, simplify the following expression:
Y = AB + A (B + C) + B (B + C)
(4 marks)
Q.2
a)
Describe the valence band, conduction band, and forbidden energy gap
with the help of energy level diagram.
(10 marks)
b)
Which are the most commonly used semiconductor materials and why.
(5 marks)
c)
What do you understand by intrinsic and extrinsic semiconductors?
(5 marks)
Q.3
a)
Draw and explain the voltage-current (V-I) characteristic of a pn junction.
(8 marks)
b)
i)
Explain with the aid of a diagram what you understand by a.c
resistance of a diode and how you can determine it from V-I
characteristic of a diode.
(6 marks)
ii)
Calculate the source current I, zener current IZ and load current IL
of a zener voltage stabilizer given that the source voltage is 40V,
VZ is 10V, RL is 2 ?
k and current limiting resistor is 3
.
?
k
How
will these values be affected if source voltage increases to 70V?
(6 marks)
Q.4
With the aid of diagrams explain the action of the following:-
a)
Full-wave
bridge
rectifier
(8
marks)
Page 2 of 3
b)
Capacitor
input
filter
(6
marks)
c)
Zener
diode
voltage
stabilizer
(6
marks)
Q.5
a)
Explain with the aid of a diagram the operation of a transistor as an
amplifier.
(5 marks)
b)
The reverse saturation current of an npn transistor in common-base circuit
is 12.5
.
A
µ for an emitter current of 20mA, collector current is 1.97mA.
Determine the current amplification factor and base current.
(4 marks)
c)
The tuned collector oscillator circuit used in the local oscillator of a radio
receiver makes use of an LC tuned circuit with LI = 58.6 µ H and CI =
300pf. Calculate frequency of oscillations.
(3 marks)
d)
Convert the binary number 110001 to its equivalent decimal number.
(4 marks)
e)
With the aid of a diagram explain the operation of an AND gate.
(4 marks)
Page 3 of 3
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