MOSFET problem

Discussion in 'Homework Help' started by tadm123, Dec 3, 2013.

  1. tadm123

    Thread Starter Member

    Nov 20, 2013
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    [​IMG]
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    The parameters of MOSFET:

    Vt=1V
    kn'=μCi=0.1[mA/V]
    λ=0.02
    L=4u
    W=20u



    Here's the formula for saturation

    [​IMG]

    I don't know where to start and I been thinking what to do for almost 1:30 hours. I tried plugging in the values into the formula and then solving for VG to get the RG values, but that doesnt' work either. What can I do to start solving this problem?
    Any help would be appreciated.
     
    Last edited: Dec 3, 2013
  2. tadm123

    Thread Starter Member

    Nov 20, 2013
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    I guess my question is what's the relationship between RG and ID
     
  3. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    497
    From my textbook, section MOSFET Small-Signal Amplifier

    "RG establishes the Q-point on the load line.

    If we assume that v_in=V_in*sin(wt), the gate-to-source voltage will have a sinusoidal signal superimposed on the dc quiescent value. As the gate-to-source voltage changes over time, the Q-point will move up and down the line.
    Moving up and down the load line translates into a sinusoidal variation in the drain current."




    So. RG sets up the Q-point. Then everything else oscillates around that point.
     
    Last edited: Dec 3, 2013
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  4. WBahn

    Moderator

    Mar 31, 2012
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    (Q1) What's the relationship between Vg and Id?

    (Q2) What's the relationship between Rg and Vg?
     
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  5. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    In saturation we use this equation to find Id current

    \Large I_{D} = \frac{1}{2}\mu_n C_{ox} \frac{W}{L} (V_{GS} - V_{TH})^2(1 + \lambda V_{DS})
     
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  6. tadm123

    Thread Starter Member

    Nov 20, 2013
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    Thanks a lot man. I feel pretty stupid now that it was right before me eyes. Thanks again.
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    4,796
    No need to feel stupid. Sometimes we all need a nudge to see something that right in front of us. I've had more than my share of, "Doh!" moments and I'm sure I will have even more as my senility deepens! :p
     
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