1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
BE SEMESTER-IV EXAMINATION WINTER 2018
Subject Code:2140910 Date:28/11/2018
Subject Name:Digital Electronics
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1

Convert (0.6875)10 to binary equivalent number
03

Using 10's complement ,subtract (72532-3250)10
(3250-72532)10
04

State and Prove De-Morgan's theorems with necessary truth table.
07
Q.2

Prove that a positive-logic AND gate is a negative-logic OR gate.
03

Why NAND gate and NOR gate are known as universal gates? Obtain Ex-OR and Ex-NOR using NAND.
04

Write short note on error detection codes.
07
OR

Write short note on Gray code.
07
Q.3

Reduce the expression
03

Define the following general characteristics of logic families. Propagation delay time Noise Margin Fan out
Power dissipation
04

Minimize the following Boolean expression using Map and realize it using logic gates.
07
OR
Q.3

Compare K-map and tabular method of minimization.
03

Compare Counters and Registers.
04

Express the Boolean function in a sum of min-terms.
07
Q.4

Distinguish between combinational and sequential logic circuits.
03

Explain full- subtractor in brief.
04

Write short note on Multiplexers.
07
OR
Q.4

State the basic difference between synchronous and asynchronous counters.
03

Explain operation of 4 bit left shift register with necessary diagrams.
04

Differentiate between level triggering and edge triggering of flip-flops. Explain Master-Slave J-K flip-flop configuration.
07
Q.5

Define following specification of ADC Resolution Conversion time Quantization error
03

Compare between various types of ROM.
04

Explain internal organization of RAM Draw and explain with necessary block diagram the process of writing in memory and reading from memory also.
07
OR
2
Q.5

Define following specifications of DAC Resolution Accuracy Settling time Monotonicity.
03

Compare various D/A Converters.
04

Describe operation of D/A converter with binary weighted resistors.
07