MOSFET symbol

1. Aug 21, 2006

antonantal

What does the arrow in the symbol of the MOSFET indicate? I skipped the lecture when we were told this and I can't figure out myself. I mean if it were after me, I would have put that arrow to indicate the direction of the electric field, but the arrow actually points the oposite way. So what does that arrow actually stand for?

2. Aug 21, 2006

Maxwell

It denotes if the MOSFET is a PMOS or an NMOS.

3. Aug 21, 2006

antonantal

That's not what I meant. For example in the case of a BJT the arrow indicates the direction of the emitter current in forward active regime. In the case of MOSFET what does it indicate?

4. Aug 21, 2006

dlgoff

As Maxwell stated. Either P-channel or N- channel. See this http://encyclobeamia.solarbotics.net/articles/mosfet.html" [Broken].

Regards

Last edited by a moderator: May 2, 2017
5. Aug 21, 2006

antonantal

Again that's not what I'm asking.
Maybe I should put it this way: why is the arrow at the NMOS symbol directed towards the gate and the arrow at the PMOS directed away from the gate?
It must be an analogy with the direction of something. Like in the case of a BJT, the direction of the arrows for npn and pnp are put in analogy with the direction of the emitter current in forward active regime.

Last edited by a moderator: May 2, 2017
6. Aug 21, 2006

chroot

Staff Emeritus
Like electric field lines, arrows are conventionally drawn to point from P to N.

- Warren

7. Aug 21, 2006

antonantal

So what you mean is that, say for PMOS the arrow points from the channel (P region) towards the rest of the bulk (N region) in analogy with the direction of the electric field between this two regions of the bulk, which is exactly the opposite direction of the electric field initially applied between the gate and the bulk (ie the voltage between gate and bulk)?

8. Aug 21, 2006

Manchot

Well, in the abbreviated MOSFET symbols (where the body is assumed to be shorted to the source and isn't shown), the arrow indicates the direction of normal current flow in the device.

9. Aug 22, 2006

antonantal

Ok. Thanks for the help guys.

10. Sep 2, 2006

Slayer26M

Hole flow and electron flow??