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NMOS Common source DC-bias and gain

  1. Oct 7, 2014 #1
    1. The problem statement, all variables and given/known data

    VOUT, they mean DC
    2. Relevant equations
    See picture, r0 is neglected also lambda (channel modulation)

    3. The attempt at a solution

    I calculate I DS with the formule given: 0.400*(0.5)²=0.1 mA

    IOUT = 5/25000 = 0.2 mA

    So the current source has got to be 0.1 + 0.2 = 0.3mA. Thats the DC current it has to be delivered right?

    I also had to calculate the AC gain:

    gm = K (VGS - VT) = 0.4mA/V

    vin = vgs

    vout / vgs = -gm * vgs * RD = -10

    This correct?
  2. jcsd
  3. Oct 9, 2014 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    If the thing in series with the +10V supply is indeed a current source labeled ID then you computed ID correctly.

    A good first step is always to define the problem accurately.

    You also have computed the ac gain correctly.
  4. Oct 9, 2014 #3
    Yes, I was also confused about the current source symbol. :) But it is one indeed.

    Thanks for the confirmation that my calculations are correct.
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