Combination Circuits


Here we’ll be designing circuits to compare different binary numbers.  Suppose we have two numbers A & B at the input and 3 output as A>B, A=B, A<B and only one of the three outputs would be high accordingly if A is greater than or equal to or less than B.

1-bit comparator: Let’s begin with 1 bit comparator and from the name we can easily make out that this circuit would be used to compare 1 bit binary numbers. If we list all the input combinations at the input then we get the following table describing the corresponding outputs.

A             B             f (A>B)  f (A=B) f (A<B)

0              0              0              1              0

1              0              1              0              0

0              1              0              0              1

1              1              0              1              0

And now we find the equations using K-maps each for f (A>B), f (A=B) and f (A<B) as follow:

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