**Logic Gates-**

Before you go through this article, make sure that you have gone through the previous article on **Logic Gates**.

We have discussed-

- Logic gates are the basic building blocks of any digital circuit.
- There are 3 basic logic gates- AND, NOT, OR.
- Logic gates are classified as-

In this article, we will discuss about Universal Logic Gates.

**Universal Logic Gates-**

Universal logic gates are the logic gates that are capable of implementing any Boolean function
without requiring any other type of gate. |

They are called as “**Universal Gates**” because-

- They can realize all the binary operations.
- All the basic logic gates can be derived from them.

They have the following properties-

- Universal gates are not associative in nature.
- Universal gates are commutative in nature.

There are following two universal logic gates-

- NAND Gate
- NOR Gate

**1. NAND Gate-**

- A NAND Gate is constructed by connecting a NOT Gate at the output terminal of the AND Gate.
- The output of NAND gate is high (‘1’) if at least one of its inputs is low (‘0’).
- The output of NAND gate is low (‘0’) if all of its inputs are high (‘1’).

**Logic Symbol-**

The logic symbol for NAND Gate is as shown below-

**Truth Table-**

The truth table for NAND Gate is as shown below-

A |
B |
Y = (A.B)’ |

0 | 0 | 1 |

0 | 1 | 1 |

1 | 0 | 1 |

1 | 1 | 0 |

**Truth Table**

**Timing Diagram-**

The timing diagram for NAND Gate is as shown below-

**2. NOR Gate-**

- A NOR Gate is constructed by connecting a NOT Gate at the output terminal of the OR Gate.
- The output of OR gate is high (‘1’) if all of its inputs are low (‘0’).
- The output of OR gate is low (‘0’) if any of its inputs is high (‘1’).

**Logic Symbol-**

The logic symbol for NOR Gate is as shown below-

**Truth Table-**

The truth table for NOR Gate is as shown below-

A |
B |
Y = A + B |

0 | 0 | 1 |

0 | 1 | 0 |

1 | 0 | 0 |

1 | 1 | 0 |

**Truth Table**

**Timing Diagram-**

The timing diagram for NOR Gate is as shown below-

To gain better understanding about Universal Logic Gates,

**Next Article-** **Alternative Logic Gates**

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