Hello Readers, in this article we will discuss different types of logic gates with their Graphical Symbol, Truth Table, Algebraic Expression, etc. Logic gates being a fundamental element of any electronic circuit is very important to know about them.
Contents
Introduction
We all know that every digital computer works on binary digits also known as BITS (0, 1). Every computer works on 0 and 1. Since it is the fundamental unit of computing, it is necessary to manipulate them in order to use computers in an effective way. In the same consent, Logic gates come to play. In easy terms, logic gates are the fundamental units of a digital circuit that help in manipulating binary digits 0 and 1. A logic gate may take one or two inputs in order to produce one or many outputs. Generally, there are two types of logic gates.
Types of Logic Gates
There are mainly two types of logic gates. They are listed below:
- Fundamental Gates
- Derived Gates
Fundamental Gates
These are the types of gates that are fundamental i.e. the primary models of gates or digital circuits. Also, they are of different types:
- AND gate
- OR gate
- NOT gate
AND Gate
AND Gate is one of the fundamental gates that produce high logic output i.e. 1 when both the inputs are high and produces low logic output i.e. 0 when any of the inputs are low. The output produces by AND gate is the same as the arithmetical multiplication. Let F be the function and A and B be the output then the algebraic expression is given as follows:
F = A.B
The gate symbol of the AND gate is as follows:
 |
| Graphical Symbol of AND Gate |
The truth table of AND Gate is given as follows:
| A | B | F = A.B |
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
OR Gate
OR gate is one of the fundamental gates that produce high logic output i.e. 1 when any of the inputs are high and produce low logic output i.e. 0 only when both the inputs are low. The output produces by the OR gate is the same as the arithmetical addition. Let F be the function and A and B be the output then the algebraic expression is given as follows:
F = A + B
The gate symbol of the OR gate is given as:
 |
| Graphical Symbol of OR gate |
The truth table of the OR gate is given as follows:
| A | B | F = A + B |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
NOT Gate
NOT gate is a type of fundamental gate that produces high logic output when the input is low and produces low logic output when the input is high. The output produces by the NOT gate is the reciprocal of the input. Let F be the function and A be the input then the algebraic expression of NOT gate is given as follows:
F = A’
The graphical symbol of NOT gate is given as follows:
 |
| Graphical Symbol of NOT gate |
The truth table of NOT gate is given as follows:
| A | A’ |
| 1 | 0 |
| 0 | 1 |
Derived Gates
They are the types of gates that are a combination of different fundamental gates. There are different types:
- NAND Gate
- NOR Gate
- X-OR Gate
- X-NOR Gate
NAND Gate
It is a gate combined of NOT gate and AND Gate. It produces high logic output when any of the inputs is low and produces low logic output when both the inputs are high. The output produced by this gate is the reciprocal of AND Gate. Hence the algebraic expression is given as:
F = (A.B)’
The graphical symbol of NAND Gate is given as:
 |
| Graphical Symbol of NAND Gate |
The truth table of NAND Gate is given as:
| A | B | A.B | (A.B)’ |
| 0 | 0 | 0 | 1 |
| 0 | 1 | 0 | 1 |
| 1 | 0 | 0 | 1 |
| 1 | 1 | 1 | 0 |
NOR Gate
It is a gate combined of NOT and OR Gate. It produces high logic output when both the inputs are low and produce high logic output when any of the input is high. The output produced by this gate is reciprocal of the OR gate. Hence the algebraic expression of NOR gate is given as:
F = (A + B)’
The graphical Symbol of the NOR gate is given as:
 |
| Graphical Symbol of NOR gate |
The Truth table of NOT gate is given as:
| A | B | A+B | (A+B)’ |
| 0 | 0 | 0 | 1 |
| 0 | 1 | 1 | 0 |
| 1 | 0 | 1 | 0 |
| 1 | 1 | 1 | 0 |
X-OR Gate
It is a type of derived gate that produces high logic output when both inputs are not the same and produce low logic output when both the inputs are the same. Hence the algebraic expression is given as:
F = A’ . B + A. B’
The graphical symbol of X-OR Gate is given as:
 |
| Graphical Symbol of X-OR gate |
The truth table of X-OR Gate is given as:
| A | B | A’ | B’ | A’.B | A.B’ | A’.B + A.B’ |
| 0 | 0 | 1 | 1 | 0 | 0 | 0 |
| 0 | 1 | 1 | 0 | 1 | 0 | 1 |
| 1 | 0 | 0 | 1 | 0 | 1 | 1 |
| 1 | 1 | 0 | 0 | 0 | 0 | 0 |
X-NOR Gate
It is a type of derived gate that produces high logic when both the inputs are the same and produces low logic when both the inputs are not the same. Hence the algebraic expression is given as:
F = A.B + A’.B’
The graphical symbol of X-NOR Gate is given as:
 |
| Graphical Symbol of X-NOR Gate |
The truth table of X-NOR Gate is given as:
| A | B | A’ | B’ | A.B | A’.B’ | A.B + A’.B’ |
| 0 | 0 | 1 | 1 | 0 | 1 | 1 |
| 0 | 1 | 1 | 0 | 0 | 0 | 0 |
| 1 | 0 | 0 | 1 | 0 | 0 | 0 |
| 1 | 1 | 0 | 0 | 1 | 0 | 1 |
