Logic Gate

LOGIC GATE

·         The term of logic gate is used to describe a circuit that performs a basic logic

operation. It is an electronic circuit that combines digital signal according to

Boolean algebra. The logic gates also controls the flow of information that we

need.

·         Next, basic logic gates with a figure and the truth table are explained for further

information and logic operation performance.

THE AND GATE

·         An AND gate is a logic circuit that performs the AND operation on the circuit’s inputs.

·         The AND operation is performed by multiplication of 1s and 0s.

·         The Boolean expression for AND operation is

X = A∙B

·         An AND gate output will be 1 only if all inputs are 1. Otherwise, the outputs are

0 when the inputs are 1 and 0.

THE OR GATE

·         An OR gate is a logic circuit that performs an OR operation on the circuit’s inputs.

·         The OR operation produces an output of 1 whenever any input is 1 or 0.

       Otherwise, if the inputs are 0s, then the output is 0 as well.

·         The Boolean expression for the OR operation is :

X = A + B

THE NOT GATE

·         The Boolean expression for the OR operation is :

THE NAND GATE

·         The NAND gate is the combination of NOT-AND.

·         It implies an AND function with a complemented or inverted output.

·         The Boolean expression for the output of a 2-input NAND gate is

THE NOR GATE

·         The NOR gate is the combination of NOT-OR and implies an OR function with a

complemented or inverted output

·         The Boolean expression for the output of a 2-input NOR gate is

THE EXCLUSIVE – OR / XOR GATE

·         The Boolean expression for XOR gate is:

UNIVERSAL GATES

Gate that can be used to implement any gates like AND , OR and NOT or any combinationof these basic gates are called universal gates . NAND and NOR are such examples .

NAND GATE

A NAND gate ( Negated AND or NOT AND ) is a logic gate which  produces an output that is false only if all its inputs are true . Figure 4-11 illustrates the truth table and graphical symbol of NAND gate . Table 4-4 shows the NAND gate equivalents of gates such as NOT , OR , AND , and NOR .

4.3.2 NOR Gate

A NOR gate (Negated OR or NOT OR) is a logic gate which produces a HIGH output (1) results if both the inputs to the gate  are LOW (0);a LOW  output (0) results if one or both input  is High (1).Figure 1 illustrates the truth table and graphical symbol of NOR gate.Table 1 shows the NOR gate equivalents of gates such as NOT,OR,AND and NAND.

Written by,

LIM YUE WINN

B031210081