NOR gate is one of the **universal logic gates** along with the **NAND gate**. Now, **how to make NOR gate?** **How does NOR gate work?** One can make a NOR gate by connecting an **OR gate** and a **NOT gate** in series. So, the main work of a **NOR gate is to give the inverted output of an OR gate**. Before understanding these things we need to know the basic things of s NOR logic gate. In this article, we are going to discuss the definition, circuit symbol, **Boolean** expression and truth table of NOR gate with two inputs and three inputs respectively.

**Contents in this article:**

**Definition of NOR gate****Boolean expression of NOR gate****Circuit symbol of NOR gate****NOR gate with two inputs****NOR gate with 3 inputs****Truth table of NOR gate with three inputs**

**What is NOR gate?**

A NOR gate consists of an **OR gate and a NOT gate in series**. NOR gate is a logic gate which give the output as the complement of the sum of the inputs. So, the output of a NOR gate is the complement of the output of an OR gate with same inputs. Therefore, **NOR gate is the inverter of OR gate**.

**Boolean expression of NOR gate**

A NOR gate can have infinite number of inputs and only one output. If **A, B, C, D**….. etc. be the inputs of a NOR gate then the **expression for the Boolean** **output** of the NOR logic is \small \textbf{Y=} \overline{\textbf{A+B+C+D}}.

**Circuit symbol for Two Input NOR gate**

This is the circuit symbol of NOR gate with 2 inputs **A** and **B**. Here, **Y** is the output. NOR gate consists of an OR gate and a NOT gate. The bubble at the head of the symbol comes from the NOT gate and rest are from the OR gate.

**Truth Table for Two Input NOR gate**

Here is the truth table for a NOR gate with two inputs **A** and **B**.

Input (A) | Input (B) | Output \small \textbf{Y=} \overline{\textbf{A+B}} |

0 | 0 | 1 |

0 | 1 | 0 |

1 | 0 | 0 |

1 | 1 | 0 |

**Truth Table of NOR gate with two inputs**

**Circuit diagram NOR gate with 3 inputs**

Here is the circuit symbol of three input NOR gate with the inputs **A, B** and **C**.

**Truth Table of NOR gate with 3 inputs**

Here is the NOR gate truth table with three inputs **A, B** and **C**. It gives the inverted output of OR gate.

Input (A) | Input (B) | Input (C) | Output \small \textbf{Y=} \overline{\textbf{A+B+C}} |

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 |

**Truth Table for three input NOR gate**

**Uses of NOR logic**

- NOR gate is one of the
**universal logic gate**. So, it can be used to develop other logic gates. - NOR gate has decent applications in memory circuit.
- The main work of NOR gate is to provide the inverted output of an OR gate.

This is all from this article on NOR gate and related facts to this gate. If you have any doubt on this topic you can ask me in the comment section.

Thank you!

**Related posts:**

**Basic logic gates – OR, AND and NOT gate****NAND gate****XOR gate****XNOR gate****Boolean algebra****Karnaugh map (K-map)**

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