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Seat No.: Enrolment No.
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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- IV EXAMINATION — SUMMER 2020
Subject Code: 2140910 Date:04/11/2020
Subject Name: Digital Electronics
Time: 10:30 AM TO 01:00 PM Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
MARKS
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Q.1 (a) Convert (53.625)10 into an equivalent binary number. 03
(b) Compare 1’s complement and 2’s complement methods. Calculate 28 -19 using 2’s complement method. 04
(c) State and prove DeMorgan’s theorems with necessary figures and truth tables. 07
Q.2 (a) Prove that a positive-logic AND gate is a negative-logic OR gate. 03
(b) Explain the characteristics of digital logic families. 04
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(c) Simplify the following Boolean expressions using K-maps: 07
(1) f=?m(1,3,5,8,9,11,15)+d(2,13)
(i) F =?M(1,2,3,8,9,10,11,14)*d(7,15)
OR
(c) Simplify the following Boolean expressions using Quine-McKluskey method: 07
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f= ABCD+ A'BCD+ AB'CD+ABC'D + ABCD'
Q.3 (a) Perform BCD addition of 91 and 81 03
(b) Compare combinational and sequential logic circuits 04
(c) Write a short note on Gray code 07
OR
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Q.3 (a) Explain even and odd parity codes. 03
(b) Design and analyze the working of a 1-bit comparator using logic gates 04
(c) Describe the working of look ahead adder circuit. 07
Q.4 (a) Explain the full adder circuit. 03
(b) Discuss the working of 3:8 decoder circuit. 04
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(c) Describe the working of 4:1 multiplexer. State the advantages of multiplexers. 07
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Q.4 OR
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(a) Differentiate between synchronous and asynchronous counters 03
(b) Explain the working of clocked RS flip-flop. 04
(c) Write a short note on applications of shift registers. 07
Q.5 (a) Explain in brief universal shift register. 03
(b) Draw and explain the circuit of R-2R ladder. 04
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(c) Write a short note on ring counter 07
OR
Q.5 (a) State the advantage of a ripple counter 03
(b) Define the following terms of DAC: 04
(1) Accuracy (ii) Resolution (iii) Linearity (iv) Settling time
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(c) Explain (1) Static RAM (ii) Dynamic RAM 07
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