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AC coupling using NMOS and PMOS

  1. Feb 20, 2012 #1
    AC coupling using NMOS

    Hello. What does AC coupling by using NMOS and PMOS actually means?
     
    Last edited: Feb 21, 2012
  2. jcsd
  3. Feb 20, 2012 #2
    Re: AC coupling using NMOS

    The drain of M2 is AC coupled by C2 to drive the load R4.

    The way the circuit work is M1 have the gate and drain shorted to set up the current which mirror to M2. The drain of M2 has positive voltage. So AC coupling is needed to bring it to ground reference level.
     
  4. Feb 21, 2012 #3
    1. The problem statement, all variables and given/known data

    The problem is to perform AC coupling by using NMOS and PMOS

    2. Relevant equations



    3. The attempt at a solution

    AC coupling by using NMOS is solved. Then I tried to build one by using PMOS, but the result from these 2 are different.

    This is the NMOS circuit:
    jl03lz.jpg

    This is the result waveform from this circuit:
    fnfmea.jpg

    This is the PMOS circuit:
    33xbj4j.jpg

    This is the result waveform from this circuit:
    15mjzhh.jpg
     
  5. Feb 21, 2012 #4

    NascentOxygen

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    Staff: Mentor

    Perhaps you'd better explain what you don't like about the second circuit. It seems to me that in both you achieved an output of 200mV p-p, so I don't see anything amiss.

    (I won't be able to help you further, but if you explain this, someone may be able to.)
     
  6. Feb 21, 2012 #5
    my question is, shouldn't the blue wave from the circuit built by PMOS has the same waveform and value as NMOS?
     
  7. Feb 21, 2012 #6

    NascentOxygen

    User Avatar

    Staff: Mentor

    Oh! The invisible blue waveform. I had not noticed it!

    I now understand your concern.
     
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