Download GTU B.Tech 2020 Summer 3rd Sem 3131704 Digital Electronics Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- III EXAMINATION - SUMMER 2020

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Subject Code: 3131704 Date: 02/11/2020
Subject Name: DIGITAL ELECTRONICS
Time: 02:30 PM TO 05:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

MARKS

Q.1 (a) Design a logic circuits for AND, OR and NOT gate using only NAND gates. 03
(b) What is the difference between demultiplexer and multiplexer? Explain with necessary diagram and truth table. 04

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(c) Explain D flip flop in detail with circuit diagram and truth table 07

Q.2 (a) Derive the SOP expression for following term 03
AB'C'+ ABC'+ AB'CD + A'BC' + AB
(b) Explain binary to gray and gray to binary conversion with circuit diagram and truth table. 04
(c) Minimize the following function using tabulation method: 07

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F(w,x,y,z)= S(0,1,2,8,10,14,15)
OR
(c) Design a logic circuit for half and full subtraction circuits with K-map equations and truth table. 07

Q.3 (a) Convert the following numbers to decimal: 03
(10101.101)₂, (330.4)₈ , (A325)₁₆

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(b) Construct 3x8 decoders with diagram and necessary truth table. 04
(c) Explain following terms with example 07
1) Inter register-transfer operation
2) Arithmetic micro operation
3) Shift micro operation

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4) Logic micro operation
OR
Q.3 (a) Draw the circuit of 3 input TTL(Transistor Transistor Logic) NAND gate and explain its operation. 03
(b) Explain working of 4-bit binary ripple counter. 04
(c) Simplify the following equation using K-map and implement using logic gates: 07

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F(A,B,C,D)= S(0,1,2,3,5,7,8,9,10,12,13)

Q.4 (a) Explain BCD adder with diagram and truth table 03
(b) Explain 1's and 2's complement with example 04
(c) Explain 2-bit UP synchronous counter with K-map equations and circuit diagram 07
OR

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Q.4 (a) Write short note on PLA. 03
(b) Reduce the expression A+B[AC+(B+C')D]=A+BD 04
(c) With neat sketch explain the operation of clocked RS flip flop with NAND and NOR gates. 07

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Q.5 (a) Convert (24)₈ into Binary. Represent the decimal number 13 in BCD. Convert (41)₁₀ into Gray code. 03

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(b) Explain 2 bit magnitude comparator with necessary diagram and equation. 04
(c) List out different types of memories used in digital logic circuits and define them. 07
OR
Q.5 (a) Explain meaning of following micro operations 03
1) T : A ? B+1

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2) T : A ? A ? B
3) T : shr A
(b) Explain BUS transfer logic for two registers 04
(c) Design a logic circuit with JK flip-flop for the given state sequence with necessary K-map equation 07

Present state Next state

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000 001
001 010
010 011
011 100
100 101

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101 000

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