XNOR GateThe XNOR gate is the complement of the XOR gate. It is a hybrid gate. Simply, it is the combination of the XOR gate and NOT gate. The output level of the XNOR gate is high only when both of its inputs are the same, either 0 or 1. The symbol of the XNOR gate is the same as XOR, only complement sign is added. Sometimes, the XNOR gate is also called the Equivalence gate. 2input ExNOR gateIt is a simple form of the hybrid gate XNOR. In this type of XNOR gate, there are only two input values and an output value. There are 2^{2}=4 possible combinations of inputs. The output level is high when both inputs are set to high(1). The Boolean expression of 2input XNOR gate is as follows:
Y=(A⨁B)'
Y=((AB)'+AB) The truth table and logic design are given below: Logic Design Truth Table
The 3input XNOR GateUnlike the 2input XNOR gate, the 3input XNOR gate has three inputs. There are 2^{3}=8 possible combinations of inputs. The Boolean expression of the logical ExOR gate is as follows:
Y=(A⨁B⨁C)' Y=(ABC)'+ABC'+AB'C+A'BC The truth table and logic design are given below: Logic Design Truth Table
ExOR gate equivalent circuitWe can form the XNOR or ExNOR gate using the gates such as AND, OR, and NOT gate. The main disadvantage of this implementation is that we use different types of gates to form a single XNOR gate. By using the NAND gates only, we can implement the ExNOR gate also. This is an easier way of producing ExNOR gate functionality. Use of ExOR gateExNOR gates are used mainly in electronic circuits that perform arithmetic operations and data checking such as Adders, Subtractors or Parity Checkers, etc. As the ExNOR gate gives an output of logic level "1," whenever its two inputs are equal, it can be used to compare the magnitude of two binary digits or numbers and so ExNOR gates are used in Digital Comparator circuits.
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