How do MOSFETs work? (P, N, and ? channel)

[csm]

I see that MOSFETs are very important electonic part of electric bicycles. There are at least two different types of MOSFET. And i believe they are like an electric gate or form of resister? I am seeking to understand how they work and are used on electric bicycles, such as controllers (and chargers or BMSs?). Any good resources out there that you can recommend? I found a couple videos, but the way the material was presented seems to be missing something. Have you found some good video tutorials that you can recommend?

Found this video tutorial on MOSFETS and transisters that is AMAZING! Except there is one thing that is not clear to me.. the tutorial said the gat pin works by sending a voltage of 0-5 volts to it. Hos is that pin grounding the voltage? What is causing a complete circuit for the Gate pin?


Here is 1 hour lecture that goes into more depth about history of transister, MOSFETs and CMOS, etc.


It is amazing and wonderful what can be found online for free.. and to learn from

[Lebowski]

a good source to learn all kinds of stuff are the MIT videos, I can really recommend everyone to go through this set:

http://ocw.mit.edu/courses/electrical-e ... -lectures/

(mosfet is explained in video 9, at minute 11)

[bigmoose]

For an N channel FET, just think of it as a voltage controlled switch. A voltage around 3 to 5 volts between the gate and the source will drop the drain to source resistance to 10's of milliohms. The gate looks like a capacitor between gate and source to the outside world.

For a P channel it works the same way except drop the gate below the source voltage by 3 to 5 volts and the drain to source resistance drops. If you take the gate beyond about 20 volts relative to the source (for most FETs) it "punches through" and blows up the FET. Think of it as an insulation failure that "arcs" over.. and "poof" you let out magic smoke.

Always remember the "body diode" caused by the intrinsic structure of the FET. There is a high power diode, typically rated nearly the same current capability as the FET from drain to source. For N channel Cathode to Drain, Anode to Source, reverse for P channel. This make as FET a great DC switch, but for AC you have to put two back to back or Source to Source.

[csm]

a good source to learn all kinds of stuff are the MIT videos, I can really recommend everyone to go through this set:

http://ocw.mit.edu/courses/electrical-e ... -lectures/

(mosfet is explained in video 9, at minute 11)

Thanks.. will check it out.