#### CBSE NOTES CLASS 12 PHYSICS

#### CHAPTER 14 SEMICONDUCTORS

**Logic gates**

A logic gate is a digital circuit that follows curtain logical relationship between the input and output voltages. They control the flow of information. The five common logic gates used are NOT, AND, OR, NAND, NOR. The logic gates can be realised using semiconductor devices.

A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels.

Logic gates are used in calculators, digital watches, computers, robots, industrial control systems, and in telecommunications.

Each logic gate is indicated by a symbol and its function is defined by a truth table that shows all the possible input logic level combinations with their respective output logic levels.