Is this correct? MOSFET general application?

Thread Starter


Joined Sep 24, 2015
I'm old school. Transistor were new when I started. So much has changed and I'm learning a lot. I believe I finally have this right. Please, have a look and tell me - in general - is this the way these things work? And don't worry about voltage, resistance or current, that part I'm comfortable with. Is my assumption in the diagram correct?

Gen MOSFET Rule.png


Joined Mar 30, 2015
You're saying THIS is correct ?
Yes. N MOSFETs turn on when the gate is more positive than the source by Vth. P MOSFETs turn on when the gate is more negative than the source by Vth. On resistance is reduced when the gate is driven harder.


Joined Mar 14, 2008
Note that the normal drain-source voltage for either polarity MOSFET is to reverse bias the substrate diode.
Otherwise the device will conduct, even with a Vgs of zero.


Joined Mar 30, 2015
Also note that the symbol used in @Jony130's post is the correct symbol for enhancement mode MOSFETs; but it's quite common for the depletion mode symbol used in your schematics to mean enhancement.

When we drew schematics at work, we didn't draw the substrate terminal or polarity arrow; and when hand drawing circuits we frequently rounded the corners so we could draw them faster.