Exclusive-NOR (XNOR) gate terminology: The statement “The Ex-NOR is sometimes called the equality gate” is ________.
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ACorrect
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BIncorrect
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CAmbiguous unless active-LOW
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DOnly true for three-input XNOR
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EOnly true for CMOS logic families
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Logic gate nicknames often reflect their truth-table behavior. The exclusive-NOR (XNOR) gate outputs a HIGH when its inputs are equal (both 0 or both 1). Because equality is exactly the condition it detects, XNOR is widely referred to as the “equality gate.” This question verifies recognition of that standard terminology.
Given Data / Assumptions:
- Two-input XNOR considered (extensions to more inputs follow parity-like rules).
- Logic HIGH indicates a match between inputs.
- Standard positive-logic conventions apply.
Concept / Approach:XNOR is the logical complement of XOR. XOR is HIGH when inputs differ; therefore, XNOR is HIGH when inputs are the same. This is equivalent to a digital equality test for two bits, thus the nickname “equality gate.”
Step-by-Step Solution:
Write XOR truth table: 00→0, 01→1, 10→1, 11→0.Complement to get XNOR: 00→1, 01→0, 10→0, 11→1.Observe that outputs are HIGH for equal pairs (00 and 11).Conclude that calling XNOR the equality gate is accurate.Verification / Alternative check:Implement equality test using basic gates: (A AND B) OR (not A AND not B) equals XNOR. This composite also returns HIGH when A equals B, reinforcing the equality behavior.
Why Other Options Are Wrong:
- Incorrect: Conflicts with the truth-table definition.
- Ambiguous/only for three-input/only for CMOS: The equality interpretation is independent of logic family and holds for the canonical two-input case.
Common Pitfalls:Confusing XOR with XNOR; overlooking that “exclusive” in XOR means “one or the other but not both.” Remember: XNOR = equal → HIGH; XOR = different → HIGH.
Final Answer:Correct