Hi,
I'm working on this Magnetic Levitation project on Arduino where i have to use a mosfet on the pwm arduino pin.
the question is: why should i use a mosfet insted of any other transistor?
The point of using it is that a mosfet can handle a pwm w/ a higher frequency than the others transistors?
I'm not sure. Please, help me!!
the schematic bellow isn't mine. I got it from, you know... internet.
A MOSFET will have a lower voltage drop and run cooler than a normal Tr (assuming correct choice of LOGIC LEVEL MOSFET).
Weedpharma
To be precise, a MOSFET is a transistor 
It's a kind of transistor. What a lot of people mean when they talk about a transistor is a BJT, another kind of transistor.
And yes, most mosfets will have a lower voltage drop so will run cooler then a BJT but in fact switch a bit slower because of the gate capacitance you have to charge.
septillion:
And yes, most mosfets will have a lower voltage drop so will run cooler then a BJT but in fact switch a bit slower because of the gate capacitance you have to charge.
Actually, switch on a bit slower.
If you saturate a BJT to achieve the lowest voltage drop, it will in fact, also switch off quite slowly (several microseconds) due to stored base junction charge.
This is the 21st century, yes you use a MOSFET! (Except at high voltage when you use an IGBT).
The BJT is really an accident of history - people were experimenting with semiconductors to find
a replacement for the thermionic valve (which is a field-effect device), and more-or-less accidentally
discovered the bipolar junction transistor. It proved easier to fabricate a useful BJT than FET so they
became the workhorse for decades, but improvements in all kinds of FET have relentlessly overtaken
the BJT in nearly every sphere of use, just as BJT's overtook thermionic valves.
For power electronics BJTs are pretty much dead in the water these days, manufacturered for spares
only I reckon.
Yeah, I remember my first transistor - CK722 back in the mid/late 50's that I purchased for about 1$ if I remember correctly (when I was earning $0.50/hour mowing lawns). Used it for an amplifier for my crystal radio. BIG step from the tubes with hundreds of volts in various places!! Interesting history on the CK722 CK722 - Wikipedia
My first MOSFETs where 2SJ48's and 2SK133's I think, about 1 ohm on resistance!
Oooh, pretty high. I use AOI514, AOI510, with milliOhm resistance.