Logic Gates 101: From AND to XNOR—Everything You Need to Know

Logic Gates 101: From AND to XNOR

—Everything You Need to Know

Logic gates:

The most important part of digital electronic circuits is the logic gate. It is 

a mechanical or electronic device that converts one or more binary inputs 

(0 and 1) into a binary output by carrying out a simple logical operation.

AND Gate:

Electronic circuits like the AND gate only produce a high output (1) when 

all their inputs are high. The AND operation is denoted by a dot (.) 

    Table:

A	B	F=A.B
0	0	0
0	1	0
1	0	0
1	1	1

    

    

    Diagram:

                

OR Gate:

An electrical circuit known as an OR gate produces a high output (1) when 

one or more of its inputs are high. The OR operation is shown by a plus 

sign (+).

    Table:

A	B	F=A+B
0	0	0
0	1	1
1	0	1
1	1	1

    

    

    Diagram:

Not Gate:

The output of an electrical circuit called a NOT gate is an inverted replica

 of the input. It is also known as inverter.

    Table:

A	~(A)
0	1
1	0

Note( Bar or ~ on A show the complement of A) 

    Diagram:

NAND Gate:

This type of gate is a NOT-AND gate, which is equivalent to an AND gate 

then a NOT gate. If any of the inputs are low, the output of the NAND gate 

is high. An AND gate with a tiny circle on the output serves as the sign. The

little circle is a representation of inversion.

    Table:

A	B	~(A.B)
0	0	1
0	1	1
1	0	1
1	1	0

    

    

    Diagram:

NOR Gate:

This is an OR gate followed by a NOT gate, or a NOT-OR gate. If any of 

the inputs are high, the output of the NOR gate is low. An OR gate with a 

tiny circle on the output serves as the sign. The little circle is a representation

of inversion.

    Table:

A	B	~(A+B)
0	0	1
0	1	0
1	0	0
1	1	0

    

    

    Diagram:

XOR Gate:

The 'Exclusive-OR' gate is a circuit that produces a high output if an odd 

number of inputs are high. To indicate the XOR operation, a plus 

sign ("⊕") is enclosed in a circle.

    Table:

A	B	A⊕B
0	0	0
0	1	1
1	0	1
1	1	0

    

    

    Diagram:

XNOR Gate:

The 'Exclusive-OR' gate is a circuit that produces a high output if an even

number of inputs are high. To indicate the XNOR operation, a plus sign 

("⊕") is enclosed in a circle with complement.

    Table:

A	B	~(A⊕B)
0	0	1
0	1	0
1	0	0
1	1	1

    

    

    Diagram: