# Logic Gates: The OR Gate

Document Reference: TN201009003 - Rev: 4.14 - Last Update: 14-11-2020 03:42 GMT - Downloaded: 22-Jun-2024 16:22 GMT

## A OR gate is a logic gate with two or more inputs and one output. One or more input states must be high to produce a high output.

### OR Gate Symbols

The inputs (`A, B`) of an OR gate are on the left, and the output (`X`) is on the right of the logic OR gate symbol.

Distinctive ShapeRectangular ShapeDIN Shape (Historic)

### OR Gate Truth Tables

#### Truth Table for OR Gate with 2 Inputs

`A``B``X`
`0``0``0`
`0``1``1`
`1``0``1`
`1``1``1`

#### Truth Table for OR Gate with 3 Inputs

`A``B``C``X`
`0``0``0``0`
`0``0``1``1`
`0``1``0``1`
`0``1``1``1`
`1``0``0``1`
`1``0``1``1`
`1``1``0``1`
`1``1``1``1`

### OR Gate Test-It

To test the gate, click the switch symbols in the image below.

### OR Gate Logical Expressions

#### Word Equation

`X = A OR B`

#### Boolean Algebra

In boolean algebra the plus sign (`+`) stands for the OR operation, e.g.:

`X = A + B`

Alternative notation:     `X = A ∨ B`

`A``B``X = A + B`
`0``0``X = 0 + 0 = 0`
`0``1``X = 0 + 1 = 1`
`1``0``X = 1 + 0 = 1`
`1``1``X = 1 + 1 = 1`
`A``B``C``X = A + B + C`
`0``0``0`X = 0 + 0 + 0 = 0
`0``0``1`X = 0 + 0 + 1 = 1
`0``1``0`X = 0 + 1 + 0 = 1
`0``1``1`X = 0 + 1 + 1 = 1
`1``0``0`X = 1 + 0 + 0 = 1
`1``0``1`X = 1 + 0 + 1 = 1
`1``1``0`X = 1 + 1 + 0 = 1
`1``1``1`X = 1 + 1 + 1 = 1

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