NAND gate
AND followed by NOT: the output is 0 only when every input is 1.
Truth table
| A | B | Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
Pins
2–8 inputs on the left, one output on the right (the bubble means inverted).
How to use it
A universal gate: any circuit can be built from NANDs alone — tie both inputs together for a NOT. Two cross-coupled NANDs make an SR latch.
Usage example
AND, then inverted: the output is 0 only when both A and B are 1 — otherwise it's lit (A = 1, B = 0 here).
Common mistakes
An unconnected input counts as 0, so a floating pin forces the output to 1.