Which type of gate outputs a logic-0 when both inputs are logic-0 or both are logic-1?

• A. And gate
• B. Or gate
• C. Xor gate
• D. XNor gate

Answer: (D)

Understanding how a two-input gate handles equal versus different inputs helps here. An XOR gate is true (logic 1) only when the two inputs differ. That means:

• 0 and 0 → 0

• 0 and 1 → 1

• 1 and 0 → 1

• 1 and 1 → 0

So it outputs a 0 when both inputs are 0 or both are 1. In contrast, an XNOR gate does the opposite: it outputs 1 when the inputs are the same and 0 when they differ. The described behavior matches the XOR gate, not the XNOR.