A circuit that responds to the relative amplitudes of two inputs, A and B, by providing a binary output, Z, that indicates A>B or A<B.

The comparator has two inputs, X, Y, and one output, Z. A comparator “compares” A to B. If A is larger than B, the output of the comparator is a “1.” If A is smaller than B, the output is a “0.” If A = B, the output Z may be undefined and oscillate between “1” and “0” wildly until that condition is removed – it may be a “1,” or it may be a “0.” It depends on how the comparator was designed. The comparator implements the following mathematical function.

If A – B > 0, then Z = 1 If A – B < 0, then Z = 0