Need help with basic CMOS circuits

Discussion in 'Homework Help' started by pghaffari, Oct 24, 2011.

  1. pghaffari

    Thread Starter New Member

    Oct 1, 2011
    13
    0
    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...

    [​IMG]

    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
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    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?
     
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