Exclusive NOR or XNOR gate

Shihab Uddin Ahmed | October 8, 2017

In the exclusive OR or XOR gate section we have seen how XOR gate works and how simple it is. Exclusive NOR or XNOR gate is also like a XOR gate, the only difference is we put a NOT logic in the output of a XOR gate and XOR gate becomes a XNOR gate. That means XNOR gate gives you inverted output of XOR gate.

Like XOR gate XNOR gate may have two and more inputs but always have one output. Let’s think about two input XNOR gate. When only one input is in logical 1 state XNOR gate output will be 0; when both inputs are in same state (either 0 or 1) output will be 1.

See the truth table below:

Truth table for two input XNOR gate photo

Truth table for two input XNOR gate

Boolean expression for XNOR gate:

Boolean expression for XNOR gate photo

XNOR gate symbol photo

XNOR gate symbol

For three or more inputs

Same principle is applicable for three or more input XNOR gates. When odd number of inputs are high output will be low.

Truth table for three input XNOR gate photo

Truth table for three input XNOR gate

XNOR gate IC

74266 (TTL) and 4077 (CMOS) are example of XNOR gate ICs. Both ICs have four two input XNOR gates. IC pin configuration is as below:

XNOR gate IC photo

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