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Topic: MOSFET for high speed PWM (Read 2258 times) previous topic - next topic

RuggedCircuits

Meh...that's a 1.5 ohm MOSFET. That's pretty high and will get very warm if carrying ~1A of current.

If you're constrained by a particular supplier, let us know what that is and perhaps we can work around this constraint.

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daveg360

I guess with such a short pulse, using multiple parallel mosfets (that are available), isn't an option?
If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

TomS

Darn, I didn't check the resistance you are right.

I am currently living in Germany and will be ordering from voelkner.de in the next few days.
If I could find a driver and mosfet there that would be great.
Unfortunately their assortment isn't too big, so conrad.de might be the alternative.

They both seem to carry a lot of transistors by "International Rectifier" so I'm now trying to find suitable mosfet from them, but no luck so far.

Dave:
I have no idea since I haven't worked with mosfets so far, but wouldn't parallel mosfets actually increase the total gate capacitance and thus be even slower?!

daveg360

I was thinking in terms of charging say 4 in parallel would be quicker than 1 large gate.  Finding suitable mosfets for the job isn't trivial though  :~
In terms of mosfet top trumps - the item that RuggedCircuits posted (STP27N3LH5) is pretty hard to beat....  I'm currently trying to design an utterly indestructible H Bridge (it's taking me forever).  I think I might use a number of those.
If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

MarkT

Quote
You are right, if you want fast, well-defined pulses you will want a combination of a low gate capacitance MOSFET and high-current MOSFET driver, like a Microchip TC4426A.


Not necessarily, for an amp or so a MOSFET driver chip is sufficient in itself (and much faster) - the MIC4422 for instance will drive several amps and has logic level input.  For a low-duty cycle application this will do without further boosting (not much power dissipation required).
[ I won't respond to messages, use the forum please ]

TomS

That's a very interesting idea Mark, thanks for pointing it out!

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