# Help stuck on homework

#### c0ldsweat

Joined Sep 20, 2005
2
The question is

(AB) + (A'B')

a. Convert the expression to an equivalent expression using only the Boolean operator NAND.

b. Diagram the circuit that realizes the expression that you just created

c. Is there a best circuit or is each better in some ways? Justify your answer with a brief discussion.

Me and my friend are stuck on part A im sure we can get the rest after that.

Thanks

#### Yeti

Joined Jul 26, 2005
35
Im thinking you could work backwards on this.

(AB)= is a AND gate right?
(A'B") = is a NOR gate right?

So (AB) + (A'B') = a AND gate and a NOR gate with their outputs going to a OR gate.

So draw the gates and substitute NAND gate equivalents. You should be able to derive the boolean equation once you get it all to jsut NAND gates.
____
(AB) = a NAND right?
and that is
(A'+B')

Hope this helps
Yeti

PS. what class is this for? I took a class that dealt with all this stuff last semester.CpE 111

#### c0ldsweat

Joined Sep 20, 2005
2
Thanks I'm still kind of confused I'm gonna ask tomorrow in class even though the HW is due oh well lol. It's for Foundations of Computer Science (COS 140) I'm a freshmen it's one of the very first classes we have to take. I should go around my dorm and ask the upper classmen engineering people they have to do it too but thanks again I'll probally be back to post again sometime soon haha.

#### aibelectronics

Joined Aug 26, 2005
24
Hi, the solution to your problem is to use de Morgan's theorem, thus:

z=z''=((AB+A'B')')'

z=( (AB)' (A'B')')'

this transforms your initial logic equation into NAND gates.
i hope that makes things clear. I don't know how to upload images, i could have easily shown you how it is done. good luck!