Combinational Circuit PYQ quiz GATE CS

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Question 1

In the following truth table, V = 1 if and only if the input is valid.
gatecs20133

What function does the truth table represent?

  • Priority encoder

  • Decoder

  • Multiplexer

  • Demultiplexer

Question 2

Consider a carry lookahead adder for adding two n-bit integers, built using gates of fan-in at most two. The time to perform addition using this adder is

  • Θ(1)

  • Θ(Log (n))

  • Θ(√ n)

  • Θ(n)

Question 3

Consider a 4-to-1 multiplexer with two select lines S1 and S0, given below

GATECS2014Q55

The minimal sum-of-products form of the Boolean expression for the output F of the multiplexer is

  • P\'Q + QR\' + PQ\'R

  • P\'Q + P\'QR\' + PQR\' + PQ\'R

  • P\'QR + P\'QR\' + QR\' + PQ\'R

  • PQR\'

Question 4

GATE2006Q35

Consider the circuit above. Which one of the following options correctly represents f (x, y, z)?

  • xz' + xy + y'z

  • xz' + xy + (yz)'

  • xz + xy + (yz)'

  • xz + xy' + (yz)'

Question 5

The switching expression corresponding to f(A, B, C, D) = Σ (1, 4, 5, 9, 11, 12) is

  • BC'D' + A'C'D + AB'D

  • ABC' + ACD + B'C'D

  • ACD' + A'BC' + AC'D'

  • A'BD + ACD' + BCD'

Question 6

In an SR latch made by cross-coupling two NAND gates, if both S and R inputs are set to 0, then it will result in

  • Q = 0, Q' = 1

  • Q = 1, Q' = 0

  • Q = 1, Q' = 1

  • Indeterminate states

Question 7

A circuit outputs a digit in the form of 4 bits. 0 is represented by 0000, 1 by 0001, ..., 9 by 1001. A combinational circuit is to be designed which takes these 4 bits as input and outputs 1 if the digit ≥ 5, and 0 otherwise. If only AND, OR and NOT gates may be used, what is the minimum number of gates required?

  • 2

  • 3

  • 4

  • 5

Question 8

Which are the essential prime implicants of the following Boolean function? f(a, b, c) = a'c + ac' + b'c

  • a'c and ac'

  • a'c and b'c

  • a'c only

  • ac' and bc'

Question 9

Consider a multiplexer with X and Y as data inputs and Z as control input. Z = 0 selects input X, and Z = 1 selects input Y. What are the connections required to realize the 2-variable Boolean function f = T + R, without using any additional hardware ?

  • R to X, 1 to Y, T to Z

  • T to X, R to Y, T to Z

  • T to X, R to Y, 0 to Z

  • R to X, 0 to Y, T to Z

Question 10

Consider the following multiplexor where 10, 11, 12, 13 are four data input lines selected by two address line combinations A1A0 = 00, 01, 10, 11 respectively and f is "the output of the multiplexor. EN is the enable input.

GATECS200227

The function f(x, y, z) implemented by the above circuit is :

  • xyz'

  • xy + z

  • x + z

  • None of these

There are 19 questions to complete.

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