Small signal analysis

Discussion in 'Homework Help' started by eazhar, Apr 13, 2007.

  1. eazhar

    Thread Starter New Member

    Mar 16, 2007
    So I'm trying to do this problem here:


    First thing I've done is figured out my small signal parameters. I cut off both of the caps and so I get:

    gm = 2*Id/Vov = 2*500u / (2-.9) = .909 mA/V
    ro = Va/Id = 50/500u = 100k

    okay then I try making my small signal model


    I forgot what to do with that current source lodged in parallel. How do i solve this circuit?
  2. farmosh203


    Nov 26, 2006
    Ebraheem, check out the example on page 293 in the textbook. It says that since Rg is very large, the current through it can be neglected. It estimates the output voltage as v_o = -gm*vgs*(R_L || r_o). So the gain is just -gm * (R_L || r_o).