Experiment 8 - The XNOR gate

Entirely analogously to the NAND and NOR gates, the XNOR gate is a combination of a XOR and a NOT gate.

A B Q 0 0 1 0 1 0 1 0 0 1 1 1 Truth Table of the XNOR logic.

XNOR symbol in circuit diagrams.

A XNOR circuit. (Enlarge)

XNOR gates in practice Though inconspicuous, the XNOR gates play a very important role in modern computing. Using this logic, a computer compares whether two numbers are identical. You recognize from truth table that the result of Q can only be equal to 1 when A and B are identical. For more see the topic Digital Comparators.

Now you have met seven gates. It is often spoken of the seven basic gates. It is therefore not always clear what is meant by "basic gates".

However, in order to confuse you completely, you will learn in the next two experiments that you really only need one basic gate.