# Dr.A.P.J.Abdul Kalam University BE III SEM ALL BRANCH DEC 2020 Digital Circuits & System [EC221] Dec - 2020 Question Paper

Dr.A.P.J.Abdul Kalam University Old Question Papers

Bachelor of Engineering

Third Semester Main Examination, Dec-2020

Digital Circuits & System [EC221]

Branch-EC

Time: 3:00 Hrs Max Marks 70

Note : Attempt any five questions. All questions carry equal marks.

Q 1 (a) Write down AND gate, NAND gate and exclusive-OR gate with suitable diagram and

truth table?

(b) Explain De-Morgan’s theorem with example?

Q.2 (a) Simplify the logic function using K-map

(b) F (A, B, C) = A’C+A’B+AB’C+BC

Q.3 (a) Express the Boolean function F = A + B’C as a standard sum of minterms?

(b) Explain full adder with truth table?

Q.4 (a) Write down half adder substractot with truth table?

(b) Explain multiplexer with suitable diagram?

Q.5 (a) What is a decoder and explain how 3*8 decoder is constructed?

(b) Explain SR flip-flop and JK flip-flop?

Q.6 (a) Write down the master-slave flip-flop?

(b) What is difference between level triggering and edge triggered?

Q.7 (a) Write down the edge triggered?

(b) Write down the Asynchronous counter?

Q.8 (a) Write short note on:

(a) PROM (b) EPROM (c) static RAM?

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