what do mosphets do?

[Overclocked_Bacon]

???

[wtfxmitchell]

deliver power

[Fetzie]

They are transistors for changing the voltage of electric current, IIRC.

[alpenwasser]

Sadly both of Wikipedia's articles on this (MOSFET, Power MOSFET) are very technical

and not at all helpful when it comes to their application in the power delivery systems

of M/B's.

I don't have time at the moment for a full rundown, but digging a bit I have

found these links which might be helpful:

• About VRMs & MOSFETs - OCN article (this looks pretty comprehensive and

  understandable from a quick glance).

• Article on hardwaresecrets about the M/B's voltage regulator circuit
• Article on Techpowerup

[juretrn]

MOSFET(metal oxide semiconductur field effect transistor) is a type of transistor- basically a semiconductor switch(not always used as a switch!)-, that works by the means of making a conductive channel due to a electric field betweeen source and drain when sufficient voltage is present on its gate. In computers, you will often see them marketed in different power regulation and delivery circuits, even though most integrated circuits are based on different permutations of the basic MOSFET design. 

I hope this is helpful to you. 

[alpenwasser]

OK, I've had a bit of time for reading up, so here's a very short and simplified version

of what I've been able to find out about this (note: I am not by any means an expert,

so if somebody spots an error feel free to point that out):

Most components on a M/B require different voltages than the PSU provides. For example,

a modern desktop CPU will need something between 1~1.5 V (usually), whereas the

main power source from the PSU for CPUs are the 8 pin EPS plugs (and their smaller

4 pin versions), which deliver +12 V relative to ground.

So basically you need a DC-DC converter to convert those 12 V to the required voltages

that can then be used to power your components (CPU, RAM, IO hub, USB and SATA

controllers, sound chips etc.), a.k.a. a switched-mode power supply.

These DC-DC converters are often called VRM (voltage regulator modules). The MOSFETS

are simply one part of these VRMs, with the other main components being PWM controllers,

chokes and a few other things.

The MOSFETs' purpose within those VRMs is to let the actual current through based on

whether or not they're switched on or off. As far as I understand things, the PWM controller

is used to control the switching frequency and duty cycle (so, how frequently are the

MOSFETs open and for how long), and this, in combination with the rest of the VRM ciruitry,

gets you the desired DC voltage you can then pass on to the CPU or whatever else you wish

to power with it.

How precisely all of this goes together is, to be perfectly honest, not something I understand

in full detail though, but I think this is very roughly how it works.

I can highly recommend the hardwaresecrets article I linked above, it should also give

you a bit more insight, especially on how power phases relate to this and a few of the

components I haven't mentioned in this post.

Also, here are a few links I came across when reading up on this, maybe some of them

might be of interest to you as well:

• http://homepages.which.net/~paul.hills/SpeedControl/Mosfets.html
• http://en.wikipedia.org/wiki/Pulse-width_modulation#Voltage_regulation
• http://www.mathworks.ch/ch/help/physmod/elec/ref/controlledpwmvoltage.html
• http://provideyourown.com/2011/analogwrite-convert-pwm-to-voltage/
• http://www.precisionmicrodrives.com/application-notes-technical-guides/application-bulletins/ab-012-driving-vibration-motors-with-pwm

[juretrn]

-helpful text-

 

Might as well use a highly detailed textbook for a university course in electronics: Donald A. Neamen: Microelectronics, it is avaliable in PDF form.

Also, allaboutcircuits is really useful with a ton of useful links to things like video lectures and more resources: http://www.allaboutcircuits.com/vol_3/chpt_2/10.html

[alpenwasser]

Might as well use a highly detailed textbook for a university course in electronics: Donald A. Neamen: Microelectronics, it is avaliable in PDF form.

Also, allaboutcircuits is really useful with a ton of useful links to things like video lectures and more resources: http://www.allaboutcircuits.com/vol_3/chpt_2/10.html

Will look into that, thanks!

I'm actually studying to be an electrical engineer, but unfortunately I'm not far

enough yet to fully understand the subject of this thread, I've just gotten a glimpse

of parts of it. Ah well, some day...

EDIT:

Also, thanks to the mod who cleaned up this thread (@Glenwing, possibly?).

[Ngrungebb91]

Well basically everyone in the thread has answered the question. I am also going to school for EET. So i'll give my little 2 cents on it. A MOSFET is a type of transistor that does not have the traditional base, common, and emitter junctions. It has drain, source, and gain junctions. When we used them in the lab, we just used them so we can see a 0v on the gate junction because that will happen if you do not have a DC PSU connected to that junction.

[kizoku_95]

MOSFET(metal oxide semiconductur field effect transistor) is a type of transistor- basically a semiconductor switch(not always used as a switch!)-, that works by the means of making a conductive channel due to a electric field betweeen source and drain when sufficient voltage is present on its gate. In computers, you will often see them marketed in different power regulation and delivery circuits, even though most integrated circuits are based on different permutations of the basic MOSFET design.

I hope this is helpful to you.

Omg if only i had read this yesterday i could have written this in my exam !!!!!!