Tag: NAND Gate 3 Input Truth Table

Universal Logic Gates | NAND Gate | NOR Gate

Digital Design

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-

 

 

  1. NAND Gate
  2. 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,

Watch this Video Lecture

 

Next Article- Alternative Logic Gates

 

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