Help on a practical example using CMOS technology

Discussion in 'Homework Help' started by wanderer, Nov 27, 2009.

  1. wanderer

    Thread Starter New Member

    Nov 21, 2009
    5
    0
    Hello,

    For a school assignment we need to show that a mosfet circuit that we build in a simulation doesn't work because it doesn't respond fast enough, but I'm lost finding a practical example that will show that the circuit will not work! The circuit is build using CMOS technology.

    Any ideas?

    Thanks in advance!!
     
  2. rogs

    Active Member

    Aug 28, 2009
    279
    37
    Can you post a schematic of the circuit?
    It's not very easy to say why a circuit will or won't work, if we don't know what the circuit is! :)
     
  3. wanderer

    Thread Starter New Member

    Nov 21, 2009
    5
    0
    I don't have the schematics here with me but the circuit its a simple logic function done with CMOS technology !( (A&!B) + (C&!D) )

    Using the delay times of the CMOS circuit for that function I have to come up with a practical example on which the circuit won't work because it doesn't respond fast enough.
     
  4. wanderer

    Thread Starter New Member

    Nov 21, 2009
    5
    0
    if needed I will try to post the schematics tomorrow...
     
  5. rogs

    Active Member

    Aug 28, 2009
    279
    37
    OK --when you say the circuit is built with 'CMOS technology' I'm guessing you mean CMOS logic gates. So one of the simplest way of describing how a specific circuit wouldn't work is to draw a circuit using 74HC logic, and then the same circuit using the equivalent 4000 series logic.

    Then using the relevant device 'family specifications' data show how the 4000 series version could be too slow for certain applications.

    A good example would be to use a 74HC4060 and select a high frequency crystal value for the oscillator part of the device (say 20MHz).
    There's no way a standard 4060 will run at 20MHz!

    you can find the relative 'family' data in the documents listed here:

    http://www.standardics.nxp.com/support/documents/logic/

    The 74HC family is the first document, the 4000 series equivalent document is about 3/4 of the way down the page.

    Hope that helps!
     
Loading...