Question

A combinational logic circuit has four inputs (a, b, c, and

d.and one output z. the output is 1 iff the input has three consecutive 0's or three consecutive 1's. for example, if a = 1, b = 0, c = 0, and d = 0, then z = 1, but if a = 0, b = 1, c = 0, and d = 0, then z = 0. design the circuit using one four-input or gate and four three-input and gates.

Answer 1

It's not possible to do it with the given gates only. If all four inputs were 0, you wouldn't be able to get a 1 from any combionation of AND gates. You have to incorporate NOR gates.