A
Logic Problem
Problem
Logic1P01
Willy Nilly needs a three-input AND gate, but he only has two input NANDS
because he only has a supply of 7400 chips. (Click
here if you want to see the pin-out for a 7400 chip.) Willy has
connected the circuit below using two, two-input AND gates.
He needs to know if the
circuit functions as a three-input AND. In other words, is the output,
F, a logical one only when all three inputs A, B and C are one? Use
the table below to help you decide. The table has a column where
you can note what the "internal variable", D, is for all combinations -
to make it easier to compute F.
|
A
|
B
|
C
|
D
|
F
|
|
0
|
0
|
0
|
|
|
|
0
|
0
|
1
|
|
|
|
0
|
1
|
0
|
|
|
|
0
|
1
|
1
|
|
|
|
1
|
0
|
0
|
|
|
|
1
|
0
|
1
|
|
|
|
1
|
1
|
0
|
|
|
|
1
|
1
|
1
|
|
|