# Correct PMOS Vgs?

Please image attached. Is there a mistake on the solutuion as it seem that for the PMOS Vgs = Vs-Vg?? Isn't it supposed to be Vgs = Vg-Vs?

Thanks

• Threshold voltage is term that is used for our convenience and its just a matter of interpretation. If you consdier Vgs of a PMOS then it would be a postive value of say -700mv but if you consider the threshold voltage as Vsg it would 700mV. In my opinion for calculations in order to maintain uniformity for N and Pmos we consider the threshold voltage to be +ve for both and thus Vsg is considered in your case to make the threshold of the Pmos a postive value . May 7 '16 at 12:58

To turn on a P-channel enhancement mode MOSFET, the gate must be taken negative with respect to the source, so $V_{gs}$ is indeed Vs - Vg although I would agree it can be misleading and would more properly be named $V_{sg}$
This yieds the absolute value of $V_{gs}$