Logic Gates
Logic gates are those physical devices which perform a logical operation. The logical operation also called switching operation. In a digital system, some basic operations performed which are simple and easier in the calculation. These operations may be required to be performed a number of times in a large digital system like a digital computer.
Electronics circuit which done the logical decisions and the process is called as logic gates. Each gate has one or more input and only one output. Some basic gates are OR, AND and NOT gates. NAND, NOR, and EX-OR are known as universal gates.
Basic gates are-
AND GATE:
The AND gate has two or more inputs and one output signal. This is a gate which performs a logical operation multiplication, which is commonly known as AND function. This gate is called an AND gate because the gate gives output will be high when all input values are high i.e., the output is high or 1 when all of the inputs are high or 1 and the output is low or 0 when any of the inputs are low or 0. The symbol of AND Gate & Truth Table is shown below.
OR GATE:
The OR gate has two or more inputs and one output signal. This is a gate which performs a logical operation or addition, which is commonly known as OR function. This gate is called an OR gate because the gate gives output will be high only if any or all input values are high i.e., the output is high or 1 when any one of the inputs is high or 1 and The output is low or 0 when both the inputs are low or 0. The symbol of OR Gate & Truth Table is shown below.
NOT GATE:
It is a gate which has a single input and a single output. It is also known as an inverter, because it does the inversion of applied binary signal i.e., when the input is high or 1 it gives output low or 0 and when the input is low or 0 it gives output high or 1. The symbol of NOT Gate & Truth Table is shown below.
NAND GATE:
The NAND gate is a gate which has two or more input terminals and one output terminals. The NAND gate is a cascade combination of AND – NOT gates. The output of NAND gate is high or 1 when any one or both the inputs are low or 0 and the output is low or 0 when both inputs are high or 1. The symbol of NAND Gate & Truth Table is shown below.
NOR GATE:
The NOR gate is a gate which has two or more input terminals and one output terminals. The NOR gate is a cascade combination of OR – NOT gates. The output of NOR gate is high or 1 when both the inputs are low or 0 and the output is low or 0 when one or both inputs are high or 1.
The symbol of NOR Gate & Truth Table is shown below.
Exclusive- OR (EX-OR) GATE:
The Exclusive gate is a gate which is used in digital data processing circuits. This gate has two or more input terminals and one output terminal. The EX-OR Gate has the output only high when an odd number of inputs are high and the output is low when both the inputs are low and both the inputs are high. The symbol of EX-OR Gate & Truth Table is shown below.
Exclusive- NOR (EX-NOR) GATE:
The EX-NOR gate has terminals like OR gate i.e, two or more input terminals and one output terminal. The EX-NOR Gate has the output only high when both the inputs have the same values either high or low and the output is low when an odd number inputs are high. The symbol of EX-NOR Gate & Truth Table is shown below.
Universal Gate
Any Boolean expression can be realized by using the AND, OR and NOT gates discussed previously. From these three operations, two more operations have been derived: the NAND operation and NOR operation. These operations have become very popular and are widely used, the reason being the only one type of gates, either NAND or NOR are sufficient for the realization of any logical expression. Because of this reason NAND and NOR gates are known as universal gates.
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