# PMOS trans-conductance formula

#### Kai Chiang

Joined Oct 27, 2015
12
This is the formula in my lecture note for NMOS
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for PMOS, is it something like this? I cant seem to find PMOS formula for this on the internet. Most of them shows the one in my lecture note

where |Vgs| = Vsg and |Vth| is VTHP
which is

#### MrAl

Joined Jun 17, 2014
8,503
Hi,

The only difference i've seen so far is the subscripts they use:
Wn, Ln for NMOS
Wp, Lp for PMOS
IDn for NMOS
-IDp for PMOS (different sign)

I think gm is positive for both because the gate voltage is probably considered negative too for PMOS, but you can check into this.