The OR gate is one of the fundamental logic gates in digital logic circuits and performs the “OR” operation. This gate ensures that the output is high (1) when at least one of the inputs is high (1). Otherwise, if both inputs are low (0), the output will be low (0).
The OR gate can accept two or more inputs and evaluates the state of each of these inputs. The output is determined as follows:
- If any of the inputs is high (1), the output will be high (1).
- If all inputs are low (0), the output will be low (0).
The truth table for this gate ;
| Input A | Input B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
4.1. What are Its Features?
- Logical Definition of Output
The mathematical definition of the output is Y = A + B (where ‘+’ represents the logical OR operation). - Scalability
The OR gate is not limited to two inputs; multi-input OR gates can also be used by combining three or more inputs. - Idempotent Property
In logical expressions, the property A + A = A holds. This means that repeating the same input does not change the output. - Commutative Property
With the property A + B = B + A, the order of the inputs does not affect the output. - Associative Property
The OR gate exhibits the property (A + B) + C = A + (B + C), meaning that the inputs can be grouped in any order for evaluation.