Logic Gates (11)

What are Basic Logic Gates?

A logic gate is a basic building block of a digital circuit that has basically two inputs and one output. The relationship between the i/p and the o/p is based on a certain logic. These gates are implemented using electronic switches like transistors, diodes. But, in practice, basic logic gates are built using CMOS technology, FETS, and MOSFET(Metal Oxide Semiconductor FET)s. Logic gates are used in microprocessors, microcontrollers, embedded system applications, and in electronic and electrical project circuits.

AND Gate

OR Gate

NAND Gate

NOR Gate

Exclusive-OR Gate

Exclusive-NOR Gate

De Morgan’s Theorem

The first theorem of DeMorgan states that the logic gate like NAND is equal to an OR gate with a bubble. The logic function of the NAND gate is

A’B = A’+B’

The second theorem of DeMorgan states that the NOR logic gate is equal to an AND gate with a bubble. The logic function of NOR gate is

(A+B)’= A’. B’

Verify with truth table for above equations. 

What are Universal Gates?

A universal gate is a logic gate which can implement any Boolean function without the need to use any other type of logic gate. The NOR gate and NAND gate are universal gates. This means that you can create any logical Boolean expression using only NOR gates or only NAND gates.