Document Reference: TN201009005 - Rev: 4.14 - Last Update: 14-11-2020 03:50 GMT - Downloaded: 01-Apr-2023 22:38 GMT
A NOR gate is a logic gate with two or more inputs and one output. All inputs states must be low to produce a high output.
NOR Gate Symbols
The inputs (A, B) of an NOR gate are on the left, and the output (X) is on the right of the logic NOR gate symbol.
| Distinctive Shape | Rectangular Shape | DIN Shape (Historic) |
|---|---|---|
 |  |  |
NOR Gate Truth Tables
Truth Table for NOR Gate with 2 Inputs
A | B | X |
|---|---|---|
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 0 |
Truth Table for NOR Gate with 3 Inputs
A | B | C | X |
|---|---|---|---|
0 | 0 | 0 | 1 |
0 | 0 | 1 | 0 |
0 | 1 | 0 | 0 |
0 | 1 | 1 | 0 |
1 | 0 | 0 | 0 |
1 | 0 | 1 | 0 |
1 | 1 | 0 | 0 |
1 | 1 | 1 | 0 |
NOR Gate Test-It
To test the gate, click the switch symbols in the image below.
NOR Gate Logical Expressions
Word Equation
X = NOT (A OR B)
Boolean Algebra
In boolean algebra the plus sign (+) combined with the overbar sign ( ) stands for the NOR operation, e.g.:
X = A + B
Alternative notations: X = A ∨ B or X = A ∨ B or X = A − B
A | B | X = A + B |
|---|---|---|
0 | 0 | X = 0 + 0 = 0 = 1 |
0 | 1 | X = 0 + 1 = 1 = 0 |
1 | 0 | X = 1 + 0 = 1 = 0 |
1 | 1 | X = 1 + 1 = 1 = 0 |
A | B | C | X = A + B + C |
|---|---|---|---|
0 | 0 | 0 | X = 0 + 0 + 0 = 0 = 1 |
0 | 0 | 1 | X = 0 + 0 + 1 = 1 = 0 |
0 | 1 | 0 | X = 0 + 1 + 0 = 1 = 0 |
0 | 1 | 1 | X = 0 + 1 + 1 = 1 = 0 |
1 | 0 | 0 | X = 1 + 0 + 0 = 1 = 0 |
1 | 0 | 1 | X = 1 + 0 + 1 = 1 = 0 |
1 | 1 | 0 | X = 1 + 1 + 0 = 1 = 0 |
1 | 1 | 1 | X = 1 + 1 + 1 = 1 = 0 |