GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER-IV (NEW) EXAMINATION - WINTER 2020
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Subject Code:2140910 Date:11/02/2021Subject Name:Digital Electronics
Time:02:30 PM TO 04:30 PM Total Marks:56
Instructions:
1. Attempt any FOUR questions out of EIGHT questions.
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2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Explain Octal to Binary encoder. 03
(b) Explain Minterm and Maxterm. 04
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(c) State and prove De Morgan’s theorems. 07 Q.2 (a) Define the following general characteristics of logic families. 03
(1) Propagation delay time (i1) Fan-in (ii1) Fan - out
(b) Draw and explain with truth table Ex-OR and Ex-NOR gates. 04
(c) Prove that NAND and NOR gates are universal gates. 07
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Q.3 (a) Explain full- subtractor in brief. 03
(b) Do as directed:- 04
I. Add the following decimal numbers using 8421 BCD equivalent codes 679.6 +536.8
II. Multiply the binary numbers (1011.01) X (10.1)
(c) Write a short note on XS-3 code. 07
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Q.4 (a) Solve: (1) (105.15)10=( )2 03
(2) (378.93)8 = ( )2
(3) (B9F.AE)16 = ( )8
(b) Explain Binary addition & subtraction with Example. 04
(c) Explain Hamming codes. A seven bit Hamming code is received as 07
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1110101. What is the correct code for even parity? Q.5 (a) Differentiate between sequential circuit and combinational circuit. 03
(b) Describe the operation of R-2R ladder D/A converter in brief 04
(c) Minimize using K-map f(A,B,C,D) = S(1,2,7,8,10,12,15) +d(0,5,6) 07
also draw MSI circuit for the output.
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Q.6 (a) What are Preset and Clear inputs with flipflop? Why are they provided 03
with flipflop?
(b) Explain operation of clocked S-R Flip-Flop. 04
(c) Describe the working of look-ahead-carry adder. 07
Q.7 (a) Design a full adder circuit using decoder and multiplexer (4:1 MUX). 03
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(b) Compare between various types of ROM. 04(c) Explain working of Successive-Approximation-Register A/D 07
converter. Compare it with Flash A/D converter.
Q.8 (a) State the applications of A to D converters 03
(b) Explain concept of shift registers 04
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(c) Explain the concept of RAM. Explain working of any one type of 07RAM.
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