$\displaystyle Vds=(R_S+R_d)*I_d+VDS$

$\displaystyle Vgs=VGS+R_S*I_d$

$\displaystyle dI_d/dVgs=g_m$

$\displaystyle dI_d/dVGS=gmo$

$\displaystyle dI_d/dVDS=gdo$

Hi,

I have a problem with finding $\displaystyle g_m$ in terms of gmo, gdo, $\displaystyle R_s$ and $\displaystyle R_d$. Does anyone know how to do this?