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Homework Help: CMOS circuit

  1. Sep 21, 2008 #1
    Hope this is the right place for this thread.

    1. The problem statement, all variables and given/known data

    Hi I need help with the truth table for a CMOS circuit.

    http://www.isk.kth.se/~william/dd/agda/bild/cmos/mos903.gif [Broken]

    2. Relevant equations

    Truth table and

    What type of circuit is this? But I guess that's easy to
    answer after setting up the truth table. Right now, I'm not even sure
    if the values for P1,p2,n1,n2 are correct.

    3. The attempt at a solution

    Is this correct?

    0 0 -> On: P1,P2, Off: N1,N2 OUT: ?
    0 1 -> On: N1,P2, Off: P1, N2 OUT: ?
    1 0 -> On: P1,N2, Off: N1,P2 OUT: ?
    1 1 -> On: N1,N2, Off: P1,P2 OUT: ?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 22, 2008 #2


    User Avatar
    Science Advisor

    I believe you're on the right track. Assuming correct biasing, application of a '1' to the gate of a NMOS will turn it on, and pull drain to ground (assuming source is at ground), while application of a '0' to the gate of a PMOS will turn it on, and pull the drain to VDD.

    The simplification here is that the output is in a push-pull configuration with PMOS and NMOS gates tied together (so it'll just invert whatever is at their shared gate).

    The (slight) complication is that the source terminals of P1 and P2 are not both connected to VDD, nor are their drain terminals both connected to the push-pull CMOSs. But just remember what the source-drain impedance of a cut-off MOSFET is.

    Hope this helps, and good luck!
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