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Introduction
A gate is defined as a digital circuit which follows some logical relationship
between the input and output voltages. It is a digital circuit which either allows a
signal to pass through as stop, it is called a gate. The logic gates are building
blocks at digital electronics. They are used in digital electronics to change on
voltage level (input voltage) into another (output voltage) according to some
logical statement relating them. A logic gate may have one or more inputs, but it
has only one output. The relationship between the possible values of input and
output voltage is expressed in the form of a table called truth table or table of
combinations. Truth table of a Logic Gates is a table that shows all the input and
output possibilities for the logic gate. George Boole in 1980 invented a different
kind of algebra based on binary nature at the logic, this algebra of logic called
BOOLEAN ALGEBRA. A logical statement can have only two values, such as
HIGH/LOW, ON/OFF,CLOSED/OPEN, YES/NO, RIGHT/WRONG,
TRUE/FALSE,CONDUCTING/NON-CONDUCTING etc. The two values oflogic
statements one denoted by the binary number 1 and 0.The binary number 1 is
used to denote the high value. The logical statements that logic gates follow are
called Boolean expressions
PRINCIPLE:
Any Boolean algebra operation can be associated with inputs and
outputs represent the statements of Boolean algebra. Although these
circuits may be complex, they may all be constructed from three basic
devices. We have three different types of logic gates. These are the
AND gate, the OR gate and the NOT gate.
Logic states
High
low
1
0
+v
0v
On
Off
Close
open
Right
wrong
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