OR as an inverted-input NAND — OR gate
exam standardthe alternative IEEE symbol
Answer
verified equivalent (both sides → B + A)
Why this example is worth doing
OR drawn as a NAND body with both inputs bubbled — De Morgan again, and the second half of the pair introduced on the AND page. The page's advice is procedural: when reading an unfamiliar schematic, first push bubbles until they cancel, then read the shapes. Doing it in the other order, reading shapes first and worrying about bubbles afterwards, is how students end up computing the complement of the circuit they were given.
Try your own input in the OR gate. Truth table, symbol and algebraic form for A + B, with a live two-input toggle.
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 | 0 |
| 1 | 0 | 1 | 1 |
| 2 | 1 | 0 | 1 |
| 3 | 1 | 1 | 1 |