PHY 308 - ELECTRONICS I EXAMINATION

NATIONAL OPEN UNIVERSITY OF NIGERIA

14/16 AHMADU BELLO WAY, VICTORIA ISLAND, LAGOS

SCHOOL OF SCIENCE AND TECHNOLOGY

MARCH/APRIL 2014 EXAMINATION

COURSE CODE: PHY 308
COURSE TITLE: ELECTRONICS I EXAMINATION
TIME ALLOWED: 2HOURS
INSTRUCTION: ANSWER QUESTION ANY FIVE QUESTIONS

QUESTION ONE

a.
i.                     Name the factors that h-parameters depends on.

ii.                     Determine the voltage gain for the circuit shown in Fig. 1, with RF = 100KΩ
and R1=10 KΩ

b.     Define the following: Mark-to-Space Ratio (MSR), Pulse Repetition Time (PRT), and Pulse Repetition Frequency (PRF).

QUESTION TWO
a.
i.            What is common-mode rejection ratio (CMRR) ?
ii.            The value of CMRR can also be expressed in logarithm term as?

b.     Calculate the input power, output power, and the efficiency of the
amplifier circuit in Figure 2 for an input voltage that results in a base current
of 10mA peak.

QUESTION THREE
a.
i.            Draw a diagram to represent a complete solid state power supply .

ii.            In the half-wave rectifier circuit of Fig. 3, determine
1.         Maximum and values of load voltage
2.       Peak values of load current
3.       Power absorbed by the load,
4.       Peak Inverse Voltage (PIV) of the diode
5.       RMS value of ripple voltage
Neglect the resistance of transformer secondary winding and that of the diode.

QUESTION FOUR
a.
i.            State three uses of multivibrator.

ii.               List the difference(s) between fixed negative voltage regulator and adjustable
voltage regulator. Give one example of each.

b.
i.            The output voltage of a three-terminal voltage regulator is 5 V @ 5 mA load, and 4.96 V at 1.5 A load. What is the regulator’s load regulation?

ii.            For the circuit below in fig 4, what is the numerical value for the two-port y-parameter
y12 . l

QUESTION FIVE
a.
i.            What is an op-amp?
ii.            State three uses of op-amp

b.

i.            With the help of a neat diagram, explain the operation of a Bridge Rectifier.

ii.            What is Peak Inverse Volatge?

Classify the following filter as active/passive and low pass/high-pass as appropriate

QUESTION SIX

a.     The Zener diode of Fig.8 has the following ratings:
VZ = 6.8 V , IZ = 50 mA @ rz = 2 W.                     IZ(min) = 5mA , IZ (max) = 150mA

What would be the load voltage when load current IL varies from 10 mA to 120
mA? Also, calculate voltage regulation of the regulator.

b.     State advantages and disadvantage of class A amplifier.

QUESTION SEVEN

a.     List the main characteristics of an ideal Op-amp.

b.     What is an Integrated Circuit ? What are its special features? Why is it so commonly used in
electronic circuits ?

c.      Sketch the CE-configuration transistor output characteristics of a transistor and
indicate the active, cut-off and saturation regions.

d.     Mention the applications of Common Emitter, Common Base and Common Collector configurations of BJT’s
You can get the exam summary answers for this course from 08039407882