Two-input NAND timing behavior (conceptual correctness check): A standard two-input NAND gate produces a LOW output only during the time interval when both inputs are simultaneously HIGH; at all other input combinations, the output remains HIGH. Is this description the correct way to judge a NAND timing diagram?

Introduction / Context:
Many textbook and lab questions present timing diagrams for logic gates and ask whether a gate “works correctly.” Even without a specific drawing here, we can state the definitive functional timing rule for a two-input NAND to determine correctness: a NAND outputs LOW only when both inputs are HIGH at the same time. This rule lets you validate any timing diagram qualitatively.

Given Data / Assumptions:

• Two-input NAND gate with ideal logic levels.
• Functional analysis (truth-based), not accounting for nanosecond-scale hazards unless specifically asked.
• Inputs are labeled A and B; output is Y.

Concept / Approach:
Truth table for NAND: A B 00→Y=1, 01→1, 10→1, 11→0. Converting to timing, Y should be HIGH except during those exact intervals when A=1 and B=1 concurrently; during those overlapping windows, Y is LOW. Therefore, a timing diagram is “correct” if it respects this mapping throughout the waveform.

Step-by-Step Solution:

Verification / Alternative check:
Use the Boolean form: Y = NOT(A · B). During any interval with A · B = 1, Y must be 0; otherwise Y = 1. This cross-checks the timing logic.

Why Other Options Are Wrong:
“Incorrect” would contradict the established NAND behavior. Options about “Schmitt-trigger” or “rise/fall times” concern analog edges and noise immunity, not the fundamental truth-function.

Common Pitfalls:
Forgetting that partial overlap matters (both need to be 1 simultaneously); confusing instant transitions with real delays; assuming glitches prove incorrect logic when they may be transient hazards outside the problem’s scope.

Final Answer:
Correct