# What is NOR Gate | Digital Electronics Tutorials | Wiki For U

Digital Electronics is branch of Electronics. Electronics students are familiar with it. Today, the all major devices that we are using are digital. The area of applications of Digital Electronics is very vast.

The logic gates is an important topic in digital electronics. They are used in very applications of electronics. NOR gate is one of them.
NOR gate is nothing but simply an OR gate connected with an inverter. It may have one, two or a number of inputs and only one output. The symbol for NOR gate is shown below:

The NOR Gate shown above is a two inputs and one output Gate. It produces high at output, when all the inputs are low or zero and it produces low or zero at output if any one input is high or 1. The truth table of NOR Gate is given below:

As shown above in truth table that When both inputs A and B are low, then NOR gives high or 1 at output.
When one is low and other is high (i.e. When A is low and B is high), it gives low or zero at output.
When both inputs are high or one, it gives zero or low at output.
Illustration of NOR Gate:
The NOR Gate can be represented by following circuit diagram :
The three switch keys shows three inputs. The bulb named X at right side shows output.
The input is one, when the switch key is closed and input is high or one when the switch key is is opened . When bulb will glow it shows one or high at output and when its closed it shows zero or low at output.

Boolean Expression for NOR Gate:
The operation of NOR Gate can also be expressed in boolean expression as:
_____
X = A + B

This expression can be read as:
X is equal to A or B NOT.
This means that the output of NOR gate i.e. X is not one or high when both inputs(A and B) are high or one.