GATE Digital Logic 2

Question 1

Which Boolean expression represents the output of an XNOR gate with inputs A and B?

Accepted Answer

A·B + A'·B'

Answer

XNOR outputs 1 when both inputs are equal, expressed as A·B + A'·B'.

Question 2

A 4-bit ripple carry adder adds two 4-bit numbers. What is the maximum number of gate delays for carry propagation?

Accepted Answer

8

Answer

Each full adder introduces 2 gate delays for carry, so 4 stages yield 8 gate delays total.

Question 3

The minimum number of NAND gates required to implement the function F = A·B + C is:

Accepted Answer

3

Answer

F = A·B + C can be realized with 3 NAND gates: NAND(A,B), NAND(C,C), and NAND of their outputs.

Question 4

In a JK flip-flop, what is the output when J=1, K=1 and a clock pulse is applied?

Accepted Answer

Q toggles to complement

Answer

When J=K=1, the JK flip-flop toggles its output on each clock pulse.

Question 5

Which of the following is a universal gate?

Accepted Answer

NAND

Answer

NAND (and NOR) are universal gates because any Boolean function can be implemented using only NAND gates.

(GATE) Graduate Aptitude Test in Engineering Practice Test