Practical Applications of Logic Gates | NOT | AND | OR | XOR | 12th Standard | TRUTH TABLE | LAB
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A logic gate is an electronic circuit which functions based on digital signals. The logic gates are considered as the basic building blocks of most of the digital systems. It has one output with one or more inputs. There re three types of basic logic gates: AND, OR, and NOT. The other logic gates are Ex-OR, NAND, and NOR. They can be constructed from the basic logic gates.
Digital electronics deals with logical operations. The variables are called logical variables. The operators like logical addition (+) and logical multiplication (.) are called logical operators. When the logical operators (+, .) operate on logical variables (A, B), it gives logical constant (Y). The equation that represents this operation is called logical statement.
For example,
Logical operator: +
Logical variable: A, B
Logical constant: Y
Logical Statement: Y = A + B
The possible combinations of inputs and the corresponding output is given in table called truth table. The circuits which perform the basic logical operations such as logical addition, multiplication and
inversion are discussed below.
AND gate
It is a logic gate and hence A, B, and Y can have the value of either 1 or 0.
Boolean equation:
Y = A.B
It performs logical multiplication and is different from arithmetic multiplication.
Logic operation
The output of AND gate is high (1) only when all the inputs are high (1). The rest of the cases the output is low. Hence the output of AND gate is high (1) only when all the inputs are high. It is represented in the truth table
OR gate
A and B are inputs and Y is the output.
Boolean equation:
A+ B=Y
It performs logical addition and is different from arithmetic addition.
Logic operation
The output of OR gate is high (logic 1 state) when either of the inputs or both are high.
NOT gate
A is the input and Y is the output.
Boolean equation
Y = A
Logic operation
The output is the complement of the input. It is represented with an overbar. It is also called as inverter. The truth table infers that the output Y is 1 when input A is 0 and vice versa.
NAND gate
A and B are input and Y is the output.
Boolean equation
Y = A.B
Logic operation
The output Y equals the complement of AND operation. The circuit is an AND gate followed by a NOT gate. Therefore, it is summarized as NAND. The output is at logic zero only when all the inputs are high. The rest of the cases, the output is high (Logic 1 state).