Elenco Understanding Logic Gates and Circuits - Manual (Page 23)

U19 U15
Project 14: Comparator
Details of the Comparator Block Diagram and Logic Chart on Next Page.
This circuit demonstrates how a comparator works. Turn the slide switch (S1) on. When the loose ends
of the red and black wires are connected to the same input (either 1 or 0), the red LED will be on
(indicating the inputs are the same). When the loose ends of the red and black wires are connected to
different inputs (one to 1 and the other to 0), the red LED is off (indicating the inputs are different).
Can you think of a much simpler circuit than the one above that achieves the same result (hint: it can
be done with just 2 gates)?
U16
1
U15 U16
1
1 1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
3 3
3
2
3
3
1
1
2
2
2
2
2
2
3
2
2
2
3
2
3
A
B
2
3
23
1
0
1
5 3
4 1
2
2 Q