Start with the smallest comparison

Make the comparison as small as possible. A and B will each be a .

That leaves only four possibilities:

• A=0, B=0equal
• A=0, B=1B is bigger
• A=1, B=0A is bigger
• A=1, B=1equal

Only one combination makes A bigger.

The circuit should output 1 for A=1, B=0. It should output 0 for the other three.