Document Reference: TN201009003 - Rev: 4.14 - Last Update: 14-11-2020 03:42 GMT - Downloaded: 23-Apr-2021 01:58 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 Shape | Rectangular Shape | DIN 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 |