An EX-NOR gate is an EX-OR gate followed by NOT gate. The basic EX-NOR gate is a two input and one output logic circuit in which the output is ‘1’ only when both the inputs are same. Thus, it is also called “gate of equivalence” or “coincidence logic”.
The logic symbol and the truth table of a two input EX-NOR gate are,
Practically, three or more variable EX-NOR gate does not exist. However if number of variables have to be EX-NORed then a number of two variable EX-NOR gates will be used in which the output is ‘1’ when even number of input variables are 1. Thus it is also known as “even number of 1’s detector”. When the number of input variables are odd then it is also known as “odd number of 1’s detector”.
