CS/B.TECH(N)/EVEN/SEM-4/4419/2024-2025/I124
MAULANA ABUL KALAM AZAD UNIVERSITY OF TECHNOLOGY, WEST BENGAL
Paper Code : PC-EE 402/PC-EEE 402 Digital Electronic
UPID : 004419
Time Allotted : 3 Hours
Full Marks :70
The Figures in the margin indicate full marks.
Candidate are required to give their answers in their own words as far as practicable
Group-A (Very Short Answer Type Question)
1. Answer any ten of the following :
(I) Convert binary 111111110010 to hexadecimal.
(II)
(III)
[ 1 x 10 = 10 ]
Draw a combinational logic circuit which can compare whether two bit binary numbers are same or not.
A negative edge-triggered flip-flop will accept inputs only when the clock is LOW.
1. True
2. False
(IV)
A 4-bit R/2R digital-to-analog (DAC) converter has a reference of 5 volts. What is the analog output for the input
code 0101.
(V) The condition occurring when two or more devices try to write data to a bus simultaneously is called ________.
(VI) When used with an IC, what does the term "QUAD" indicate?
(VII) Minimum how many OR gates are required for a Decimal-to-BCD encoder?
(VIII) How is a J-K flip-flop made to toggle?
(IX) What is the role of sample-and-hold circuits in analog-to digital converters (ADCs)?
(X)
(XI)
(XII)
The practical use of binary-weighted digital-to-analog converters is limited to______________ bit D/A converter
What do you understand by 'active high' and 'active low' in digital electronics?
What does LS in 74LS00 indicate?
Group-B (Short Answer Type Question)
Answer any three of the following :
[ 5 x 3 = 15 ]
2.
3.
4.
5.
What is an encoder? How does a priority encoder differ from a conventional encoder?
Write short note on: Random Access Memory
Give an analytical overview on nonlinearity (NL) and differential nonlinearity (DNL) of A/D converter.
Why do we need to have secondary storage devices when the computer already has a primary
storage?
6. What are counters with arbitrary count sequences? Designing a counter with a given arbitrary count
sequence.
Group-C (Long Answer Type Question)
Answer any three of the following :
[5]
[5]
[5]
[5]
[5]
[ 15 x 3 = 45 ]
7. Write down Boolean expressions representing the SUM and CARRY outputs in terms of three input
binary variables to be added. Design a suitable combinational circuit to hardware-implement the
design using NAND gates only.
8. a) The 100 kHz square waveform given below is applied to the clock input of the flip-flops shown in the
following figures. If the Q output is initially ‘0’, draw the Q output waveform in the two cases. Also,
[ 15 ]
[ 10+5 ]
1/2
determine the frequency of the Q output in the two cases.
b) With the help of the logic diagram, describe the operation of a clocked R-S flip-flop with active LOW R
and S inputs.
9. Briefly describe the following with reference to D/A converters:
(a) a multiplying-type D/A converter;
(b) a companding-type D/A converter;
(c) Bipolar-Output D/A Converters;
(d) the current steering mode of operation;
(e) the voltage switching mode of operation
3 X 5 = 15
10. With the help of a block schematic, describe the role of various elements in a computer system.
Explain in brief the concept of cache memory.
9+6
11.
[ 15 ]
[ 15 ]
[ 15 ]
The above figure shows the internal logic circuit diagram of one of the four D latches of a four-bit D
latch in IC 7475. (a) Give an argument to prove that the Q output will track the D input only when
the ENABLE input is HIGH. (b) Also, prove that the Q output holds the value it had just before the
ENABLE input went LOW during the time the ENABLE input is LOW.
8+7
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