Gate behavior under mixed inputs Which logic gate has a LOW output whenever any one (or more) of its inputs is HIGH?

Introduction / Context:
Recognizing the input–output relationship of basic logic gates is crucial for troubleshooting digital circuits and for converting truth tables into gate implementations. NOR gates are especially important because they are universal—any logic function can be built from NOR gates alone.

Given Data / Assumptions:

• Standard positive logic is assumed (1 = HIGH, 0 = LOW).
• The gate output is LOW if any input is HIGH.
• No tristate or open-collector behavior is involved.

Concept / Approach:

A NOR gate performs logical OR followed by inversion. Thus, Y = NOT(A + B + ...). The OR inside becomes 1 if any input is 1; the inversion then forces the output to 0 in that case. Therefore, only when all inputs are 0 does the output become 1; otherwise it is 0 (LOW).

Step-by-Step Solution:

Verification / Alternative check:

Consulting the NOR truth table shows the output is 1 only for the all-zeros input combination; for any other combination containing a 1, the output is 0. This exactly matches the statement in the question.

Why Other Options Are Wrong:

• NAND outputs HIGH when any input is LOW; it is not LOW upon a single HIGH unless all inputs are HIGH.
• AND outputs LOW when any input is LOW, not HIGH.
• OR outputs HIGH if any input is HIGH, the opposite behavior.
• XOR outputs HIGH when an odd number of inputs are HIGH, not “any one”.

Common Pitfalls:

• Confusing NOR with NAND. Remember: NOR is OR-then-invert; NAND is AND-then-invert.

Final Answer:

NOR gate