Concepts

Computer Science - Class 11
Chapter 12 Class 11 - Boolean Algebra

## Logic Gates

A logic gate is simply an electronic circuit which takes one or more electronic signals as input to give an output signal.

## Basic Gates

### NOT Gate

• It is an inverter circuit which has only one input signal and one output signal.
• It gives the complement of the input as the output.
• Symbol:

### AND Gate

• It can have two or more input signals, but only one output signal.
• If any of the input is 0, output is 0.
• If all the inputs are 1, then the output is 1.
• Symbol:

### OR Gate

• It can have two or more input signals, but only one output signal.
• If any of the input is 1, output is 1.
• If all the inputs are 0, then the output is 0.
• Symbol:

## Universal Gates

### NOR Gate

• It can have two or more input signals, but only one output signal.
• It is an inverted OR gate.
• If any of the input is 1, output is 0.
• If all the inputs are 0, then the output is 1.
• Symbol:

### NAND Gate

• It can have two or more input signals, but only one output signal.
• It is an inverted AND gate.
• If any of the input is 0, output is 1.
• If all the inputs are 1, then the output is 0.
• Symbol:

## Special Gates

### XOR Gate

• The XOR( Exclusive OR ) gate can have two or more input signals, but only one output signal.
• If the input has an odd number of 1’s, output is 1 otherwise the output is 0.
• Its algebraic symbol is
• Symbol:

Q = A ⊕ B = (A’.B + A.B’)

### XNOR Gate

• The XOR( Exclusive NOR ) gate can have two or more input signals, but only one output signal.
• If the input has an even number of 1’s, output is 1 otherwise the output is 0.
• Its algebraic symbol is
• Symbol:

Y = A ⊙ B = (AB)’ + AB

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.