Exclusive-NOR gate is formed by combining the Exclusive-OR gate (XOR gate) and the NOT gate. On analysing the truth table of Exclusive-NOR gate, we understand that the output is similar to the standard NOR gate except that the output of the Ex-NOR gate is high when both inputs are high. The output of EX-NOR gate is 1 when both the inputs are 1 (high) and if both the inputs are 0 (low). If either one of the input is 1 (high) the output will be 0 (low). In other words, both the inputs should be in the same logic level for the output to be 1.
Symbol and Boolean expression for NOR gate
The logic symbol of an Exclusive-NOR gate is an XOR gate (Exclusive-OR gate) with the “inversion bubble” or the circle in front. Therefore, the Exclusive-NOR gate is the complementary form of the Exclusive-OR gate. The Boolean expression for the Exclusive-NOR gate is given by
Truth table for 2-input Ex-NOR gate
The same logic can be used to find the output of 3 input Ex-NOR gate. The Boolean expression for the same is given by
. The truth table for 3 input is given below
Truth table for 3-input Ex-NOR gate
Exclusive-NOR gate equivalent circuit
The Ex-NOR gate can be constructed by combining the OR gate, AND gate and NOT gate.
One easier way of constructing the Ex-NOR gate is from using a single gate like the AND gate.
Application of Exclusive-NOR gate
Some of the application of Ex-NOR gate is in
- Encryption and arithmetic circuits
- Error-detecting circuits to find odd parity and even parity in digital data transmission.