MOSFET problem

Discussion in 'Homework Help' started by chintu84, Nov 15, 2006.

  1. chintu84

    Thread Starter New Member

    Oct 18, 2006
    6
    0
    Parameters: VTn = 0.75, Kn = 25 uA/V2, lambda = 0.05 V-1, Vdd = 10 V.
    Calculate the output impedance (the total impedance as seen from the node labeled Vo) of this circuit, if IDS is 1.2 mA.
    Express your answer in Ohm, accurate to 1 Ohm.
    I have attached the circiut for this problem and i have been tring to solve this problem for 4days, and i hav got the answer as 2/gm, but the answer was wrong when i substituted the values.
    can any one help me to solve this problem.
    i have tried using small signal analysis.
     
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Could you post your attempt in steps please?
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    143
    Posting your attempts at the small signal analysis would help. I take it you have modelled M2 as a resistor in the small signal model?

    Dave
     
  4. chintu84

    Thread Starter New Member

    Oct 18, 2006
    6
    0
    i got the out put impedance to be

    Ro=Rs+ro(1+(gms+gmbs)Rs)

    Rs=Vs/Ids

    ro=1/lambda*gms*vs
     
  5. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    143
    Sorry to be picky, but can you post the small-signal model circuit that you performed the above analysis on? The suitability of your equations is dependant on the circuit you perform the analysis on.

    Dave
     
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