looking for mosfet tutorials

[large_ghostman]

hi i am on the look out for mosfet tutorials, video would be good but dosnt have to be, i have watched a few on you tube and they range from utterly rubbish and incorrect to mainly bable on P and N junction's, i get P and N junction's that isnt the issue, what i am after is a tutorial that explains the parameters that are found in datasheets and how they relate to the operation of a mosfet. so are there any that anyone would particularly recommend? a while back i found one buy a guy that was really good he had alot of electronic video's (it wasnt afrotechmod although he is pretty good as well) i didnt get to watch it all and didnt book mark it and now cant find any of his stuff.
so if you have a vid you think is a good tutorial can you post a link please.Like i said i am not after the how to switch a motor on type video more a technical explanation of what the different parameters mean in a datasheet and how to apply them to a design
many thanks
LG

 

[jpanhalt]

I have not seen anything labeled "tutorial." In fact, I am not sure what line separates a tutorial from an application note.

Here is a list of application notes I found useful. I recommend the first, as the most general. The last specifically covers the gate resistor.

http://www.irf.com/technical-info/appnotes/an-937.pdf
http://www.irf.com/technical-info/appnotes/an-978.pdf
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John

 

[dr pepper]

I havent seen one either, I had to find out a load of that from different sources.

Particular specs to look out for are:
Vds
Rds on resistance
Qg gate charge

You'll find the former affects the latter.

What do you intend to do with fets, switch, amplify or are you just reading up.

 

[large_ghostman]

i intend to switch a slightly larger fanj with one but main point is just reading and learning because i try and keep away from fets simply because i dont understand how to get them to operate properly, seems silly so i am doing something about it, i read the links but its a bit over my head the main trouble, is the first one dosnt label the pins and i get drain and source mixed up!!
Drives me mad that drain and source are opposite to what logic tells me they should be, alot of places use the water tap analogy for fets and that makes it worse. When i look at a fet i think the source should be the tap because thats where the water comes from and the drain should be a drain/plughole and thats where the water goes to!
but its wrong so once i can get that sorted in my head the same way it is with transistors i am away the other thing i found hard was they didnt actually draw in the resistor's and for me at this point i need to see them to fix it all in my head so i will redraw them. But apart from those niggles they are packed full of info!
what i am wanting is too learn about how and when to use thngs like bootstrapping, what exactly RDson is (although i think i now get that, i am thinking because part of the fet channel when its on acts like a resistor its the resistance between Drain and Source (the channel bit??) when the fet is fully on). but main thing is to learn what all the parameters are and what they mean and how they affect function of the device! FETS are a big one for me so i have given myself a couple of weeks to nail the suckers
a list of question will appear soon lol

 

[large_ghostman]

i am on mums laptop this morning so i dont have any schematic software on here except LT spice (i sneaked it into the programs folder ) i am going to try and sim some stuff with MOSFETS this morning, so a good time to start learning LTspice, i will see if there is a IRF530N model, i have a few of them that are sealed so i know they are good and not toast.

 

[dr pepper]

Your right about rds, if the voltage on the gate is higher than the gate threshold the fet acts as a resistor, usually a very low value one.
If your just switching a fan on/off you can use a fet just like a power trans, omit the base resistor and put a 1k or so to ground on the gate to keep it pulled down.
You need to worry about gate capacitance and charge etc when your switching at khz or these days 100's of khz.
I cant be bothered with 'official' analogies, I remember them as a comparison to bipolars, drain - collector, gate - base, source - emitter, on a lot of circuits they are laid out in a similar fashion.
You should wear your wrist strap with some fets, they are static sensitive, that said I havent blown one yet.

 

[large_ghostman]

i seem to carry alot of charge! but i do have a mat and wrist strap i wear via a 10meg resistor to earth via a plug socket