# Need help with basic CMOS circuits

#### pghaffari

Joined Oct 1, 2011
13
Problem:
Show a CMOS circuit for network depicted in Figure 3.21 using:
a) AND and NOR circuits
b) one complex gate

basically, the figure gives you the following switching expression: (abc + d)'

My question now is how do I do a and b. I understand how to implement this into a basic cmos circuit using pmos and nmos. It would look like the following.

http://imageshack.us/g/846/26204024.jpg/

My question is .. how do i go from the first picture to the 2nd picture which is the answer... I have a midterm on this at the end of the week so I need as much description as possible. I tried reading the book but its very confusing, hopefully someone here can clear it up for me. Thanks

#### Georacer

Joined Nov 25, 2009
5,181
The question states that you should form only NAND and NOR circuits.

(abc+d)' means that you should have a circuit that in its PDN will have (abc+d). But since you can perform only NAND or NOR operations you should create the abc signal beforehand.

Let x=abc. That will transform the final expression into (x+d)' which is the rightmost part of the picture.
In order to create x, we need to build the following: x=abc=((abc)')', since we need to form NAND networks.

In essence this is what the picture does. Create (abc)', invert it, and the NOR it with d.

Is that clear?