PHYS345 Electricity and Electronics

Answer for P9.5

Schematic of 4 NAND gates

    (A.B)' (A.D)' (B.D)' (E.F)'
A B D E F C
0 0 1 1 1 0
0 1 1 1 0 1
1 0 1 0 1 1
1 1 0 1 1 0

The NAND combination is one way to make an XOR gate.

Answer for S9.2

First gate combination

      B.C A+E  
A B C E D
0 0 0 0 0
0 0 1 0 0
0 1 0 0 0
0 1 1 1 1
1 0 0 0 1
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1

Second gate combination

      A+B A+C F.G
A B C F G D
0 0 0 0 0 0
0 0 1 0 1 0
0 1 0 1 0 0
0 1 1 1 1 1
1 0 0 1 1 1
1 0 1 1 1 1
1 1 0 1 1 1
1 1 1 1 1 1

The final column for C in each case is the same, thus the gate combinations are equivalent.

Answer for P9.5

original circuit
The original circuit

DeMorgan's theorem applied
After application of DeMorgan's theorem

NOT bubbles moved
NOT bubbles moved to identify NAND gates

inverter from NAND
Isolated NOT operation formed from NAND inverter

Answer for P9-10

Each gate is an XOR gate.


"http://www.physics.udel.edu/~watson/phys345/protected/exercises/answers/1027.html"
Last updated Nov. 20, 1998.
Copyright George Watson, Univ. of Delaware, 1998.