# Know about Basic Logic Gates with Truth Tables

Nowadays, computers have become an integral part of life as they perform many tasks and operations in quite a short span of time. One of the most important functions of the CPU in a computer is to perform logical operations by utilizing hardware like Integrated Circuits, electronic circuits and software technologies. But, how these hardware and software perform such operations is a mysterious puzzle. In order to have a better understanding of such a complex issue, we must have to acquaint ourselves with the term Boolean Logic, developed by George Boole. For a simple operation, computers utilize binary digits rather than digital digits. All the operations are carried out by the Basic Logic gates.

## What is Logic Gate

A logic gate is a basic building block of a digital circuit that has two inputs and one output.The relationship between the i/p and the o/p is based on a certain logic. These gates are implemented using electronic switches like transistors, diodes. But, in practice basic logic gates are built using CMOS technology, FETS and MOSFET(Metal Oxide Semiconductor FET)s. Logic gates are used in microprocessors, microcontrollers, embedded system applications and in electronic and electrical project circuits. The basic logic gates are categorized into seven: AND, OR, XOR, NAND, NOR, XNOR and NOT. These logic gates with their logic gate symbols and truth tables are explained below.

#### AND Gate

The AND gate is a digital logic gate with ‘n’ i/ps one o/p, which perform logical conjunction based on the combinations of its inputs.The output of this gate is true only when all the inputs are true. When one or more inputs of the AND gate’s i/ps are false, then only the output of the AND gate is false. The symbol and truth table of an AND gate with two inputs is shown below.

#### OR Gate

The OR gate is a digital logic gate with ‘n’ i/ps and one o/p, that performs a logical conjunction based on the combinations of its inputs.The output of the OR gate is true only when one or more inputs are true. If all the i/ps of the gate are  false, then only the output of the OR gate is false. The symbol and truth table of an OR gate with two inputs is shown below.

#### NOT Gate

The NOT gate is a digital logic gate with one input and one output that operates an inverter operation of the input.The output of the NOT gate is the reverse of the input. When the input of the NOT gate is true then the output will be false and vice versa. The symbol and truth table of a NOT gate with one input is shown below. By using this gate, we can implement NOR and NAND gates

#### NAND Gate

The NAND gate is a digital logic gate with ‘n’ i/ps and one o/p, that performs the operation of the AND gate followed by the operation of the NOT gate.NAND gate is designed by combining the AND and NOT gates. If the input of the NAND gate high, then the output of the gate will be low.The symbol and truth table of the NAND gate with two inputs is shown below.

#### NOR Gate

The NOR gate is a digital logic gate with n inputs and one output, that performs the operation of the OR gate followed by the NOT gate. NOR gate is designed by combining the OR and NOT gate. When any one of the i/ps of the NOR gate is true, then the output of the NOR gate will be false. The symbol and truth table of the NOR gate with truth table is shown below.

#### Exclusive-OR Gate

The Exclusive-OR gate is a digital logic gate with two inputs and one output. The short form of this gate is Ex-OR. It performs based on the operation of OR gate. . If any one of the inputs of this gate is high, then the output of the EX-OR gate will be high. The symbol and truth table of the EX-OR are shown below.