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Calculate the Transconductance for a MOSFET, given W,L,Vg,Vd,u,Cox but not Vth

  1. Aug 23, 2011 #1
    1. The problem statement, all variables and given/known data

    This problem is given to me by programme inductor, and I just copy the whole description here so every given element is the same as what he/she gives. I'm confused with the given conditions.

    1) What is the transconductance (gm) of a MOSFET biased at W=L=1um,
    uCox=0.01A/V^2, Vg= 1V and Vd=1V?

    2) For the same transistor with a load resistance of 100ohm, what is the
    voltage gain?

    2. Relevant equations

    Triode mode or linear region, When VGS > Vth and VDS < ( VGS – Vth )

    [tex]I_D=\mu_nC_{ox}\frac{W}{L}((V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2})[/tex]

    Saturation or active mode, When VGS > Vth and VDS > ( VGS – Vth )

    [tex]I_D=\frac{\mu_nC_{ox}}{2}\frac{W}{L}(V_{GS}-V_{th})^2(1+\lambda (V_{DS}-V_{DSsat}))[/tex]

    or

    [tex]I_D \approx \frac{\mu_nC_{ox}}{2}\frac{W}{L}(V_{GS}-V_{th})^2 [/tex]

    The derivation is http://ecee.colorado.edu/~bart/book/book/chapter7/ch7_3.htm" [Broken].

    3. The attempt at a solution

    I'm afraid the threshold voltage Vth should be given to do the calculation, besides, Vg=Vd=1V here so the transistor should be in Saturation Mode , should I assume the value of Vth by myself or just assume that Vg-Vth is approximately equal to Vd ?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
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