Logic gates are the electronic circuit which makes logic decisions. There are two algebric values which are used for the two posible conditions of logic gates 0 and 1. These two conditions are named according to the present situations. They are known as positive and negative, high and low, true and false, on and off and closed and open etc.

Basically, there are three types of logic gates and the other types are derived from these three basic types.

1     OR GATE            2 AND GATE           3 NOT GATE

 

1 OR GATE :

                     It has two inputs and one output. A simple diagram of or gate is given below. Its output is one only when both of its inputs are 0. Otherwise it output will be 1. Its truth table and mathamatical expression is given below.

                                 X =   A + B

  

 

2     And gate:

                 It has also two inputs and one output. A simple diagram of and date is given below. Its value is one only one when both of inputs are one. Otherwise output will be zero. Its truth table and mathamtical expression is given below.

                             X   = A . B

 

 

3     NOT GATE:

                   It has only one input and one out put. It is a reverse gate which has been shown by a bar on the value. A simple diagram of not gate is given below. Its input is one when output is zero and input is zero when output is one. Its truth table and mathamatical expression is given below.

                                 X   =   A