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Topic: From Arduino output to the gate of the MOSFET? (Read 627 times) previous topic - next topic

oransen

For driving a white LED at a 9V DC power supply I've found that a 220 Ohm resistor in series with the LED gives good results.

But from the Arduino output to the gate of the MOSFET (IRF 520) is it acceptable, advisable, to connect directly or to put some resistor in series?

I'm using a 1.5K resistor at the moment, just to be safe, but I'm no MOSFET expert so any pointers welcome.

RIDDICK

#1
Sep 15, 2009, 05:43 pm Last Edit: Sep 15, 2009, 05:44 pm by RIDDICK Reason: 1
Hey!

I read once, that a 100Ohm resistor is a good gate resistor...

The datasheet of the IRF520 says repeatedly something about a RG... it seems like they recommend 18Ohm...

I think, the gate capacitance is so low, that there wont be a high current, because of the resistance of the cable and the relatively slow transition of the arduino pin...

but i wonder if a gate voltage of 5V will decrease the resistance of that FET sufficiently...
what do u think?

bye
-Arne

Grumpy_Mike

Quote
but i wonder if a gate voltage of 5V will decrease the resistance of that FET sufficiently...
what do u think?


Yes this FET needs 10V on the gate to turn it on fully. You want to look for a 'logic level' FET, these turn on fully at 5V.

The gate resistor is to stop excessive inrush and 20R would be fine. Making it bigger just slows down the switch on speed.

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