Code: AC03/AT03 Subject:
BASIC ELECTRONICS &
Time: 3 Hours DIGITAL CIRCUITS
Max. Marks: 100
NOTE: There are 9 Questions in all.
· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.
· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.
· Any required data not explicitly given, may be suitably assumed and stated.
Q.1 Choose the correct or best alternative in the following: (2x10)
a. The mobility of
electrons in an N-type semiconductor is 
. If the resistivity of the
semiconductor is 
, then the number of electron
carriers per 
will
be,
(A)
. (B) 
.
(C) 
. (D)
.
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b. The output of comparactor is
(A) –2 V
(B) –5 V
(C) +10 V
(D) –10 V
c. Which of the following h-parameters of a transistor has the greatest value
(A)
(B)
(C)
(D)
d. If
the value of 
for the two transistors used in a Darlington amplifier are 150 and 100 respectively, then the overall current gain of the
amplifier is
(A) 14000. (B) 12000.
(C) 15000. (D) 1000.
e. The
parameters of a JFET used in a common source amplifier are : 
and 
. If the value of
the load in the drain circuit is 10
, then the voltage gain for the
amplifier is
(A) –14.5. (B) 52.5.
(C) –100. (D) –24.5.
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f. The output Y of Logic circuit is
(A) 0
(B) 1
(C) 
(D) 
g. The complement of
the Boolean expression 
is
(A)
A+BC (B)
(C) 
(D)
1
h. When 
is subtracted
from 
using
2’s complement method, the result is
(A)
. (B)
.
(C) 
. (D)
.
i. The fastest Logic family is
(A) TTL (B) CMOS
(C) ECL (D) HTL
j. How many address
bits are needed to operate a 
- bit ROM memory?
(A) 8 (B) 15
(C) 32 (D) 11
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. What is a semiconductor? How does a semiconductor behave at absolute zero temperature? Name four semiconductor materials. (6)
b. Design a 4-bit serial-in parallel out Left shift Register. (5)
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c. Determine the value of the collector
current and collector-to-emitter voltage
for the voltage divider of biasing
for the transistor shown in Fig.3.
Take
and 
for
the transistor used. (5)
Q.3 a. Describe the advantages of h-parameters? Draw
Low frequency small signal hybrid-model for a common emitter transistor and determine
Voltage gain (
),
Current gain 
,
Input Impedance 
and
Output Impedance 
.
(12)
b. For the amplifier circuit
shown in Fig.4, write the h-parameter equivalent circuit and find the current
gain for the amplifier. The transistor h-parameters are:
. (4)
Q.4 a. Draw the a.c. equivalent circuit of a JFET common-drain amplifier and derive the voltage gain of the amplifier. (8)
b. Draw the circuit diagram
of RC phase oscillator and derive the condition for oscillation. Neglect the
effects of 
and 
. (8)
Q.5 a. Draw the circuit of basic Integrator and differentiator using an op-Amp and explain its operation. (6)
b. Calculate
the output voltage for the circuit given in Fig.5. The input voltages are
and
. (5)
c. What do you mean by a Regulated Power Supply? What are the important elements of a regulated Power supply? Define the term Voltage Regulation. (5)
Q.6 a. Prove the following: 
. (5)
b. Minimize the Boolean expression given using K-map method.
(6)
c. Write the truth table and logic diagram of 1:8 demultiplexer; using NAND gates only. (5)
Q.7 a. What is a Schottky diode? Comment on the storage time of Schottky diodes. (6)
b. Explain NMOS logic circuit? Draw the circuit of an NMOS inverter that uses an n-channel enhancement-type MOSFET as a load resistor and briefly explain its operation. (10)
Q.8 a. What is ECL? Mention its characteristics. (8)
b. Write a note on programmable logic arrays. (8)
Q.9 a. Draw a static CMOS memory cell and explain it’s read and write operations. (6)
b. What do you mean by ‘STATE’ of a counter? Draw the schematic of a four-bit synchronous binary UP-Counter using T flip-flops (positive edge triggered) and briefly explain it. (10)
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