GATE 2011 CS (CS1) – Question 23
Which shown circuit is NOT equivalent to a two-input XNOR gate?
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: (D) Circuit D
Explanation
A inverts XOR. B complements both inputs before XOR and then inverts, again producing XNOR. C complements one XOR input, also XNOR. In D, set both inputs to zero: the upper NAND gives one, the lower OR receives an inverted zero and gives one, and the final NAND gives zero. XNOR at (0,0) is one, providing a counterexample. Thus D.