NOR as an inverted-input AND — NOR gate
edge casethe alternative symbol
Answer
verified equivalent (both sides → A′ · B′)
Why this example is worth doing
The De Morgan equivalent: an AND body with both inputs bubbled. In a NOR-only design these alternate with the plain NOR symbol so that bubbles pair off along each path, making the underlying OR-AND structure legible. The page shows the same three-gate network drawn both ways — all plain NOR symbols, then with alternating symbols — and the second is dramatically easier to read. That comparison is the argument for bothering with two symbols per gate.
Try your own input in the NOR gate. Truth table, symbol and algebraic form for (A + B)′, the other universal gate.
How the answer is reached
The law
(A + B)′A′ · B′— Both sides have the same truth table over the union of their variables.
Truth table
| # | A | B | F |
|---|---|---|---|
| 0 | 0 | 0 | 1 |
| 1 | 0 | 1 | 0 |
| 2 | 1 | 0 | 0 |
| 3 | 1 | 1 | 0 |