ITPEC FE Subject A April 2026 Question 17
ITPEC FE Subject A April 2026 — Question 17 of 60
NAND circuit — output is 0 only when both inputs are 1.
NAND is AND followed by inversion, giving:
| A | B | X |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
The single 0 appears exactly where both inputs are 1, matching the requirement.
Answer (b)
Why not others:
- (a) AND — outputs 1 when both inputs are 1; the exact inverse of what is asked
- (c) OR — outputs 0 only when both inputs are 0
- (d) XOR — outputs 0 whenever the inputs are equal, so it is also 0 when both are 0
Key rule: Read the requirement as a truth table row before matching a gate. "0 only when both are 1" pins down one row and rules out every gate whose zero sits elsewhere.
AI-generated — may contain errors
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