driving a MOSFET from a BeagleBoard GPIO?

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1

Hi. This seems like it should be simple, but it's giving us a bit of trouble.

I can control the GPIO (139, pin 3 of the expansion connector) just fine. The problem is that the 1.78V output doesn't seem to be enough to trigger any of the MOSFETs we've tried - most recently a BS107A. The load we're trying to drive is a bank of LEDs, drawing about 100 mA at just under 12V. With the BS107A I'm getting about 9.5V out (which isn't enough), presumably because the MOSFET isn't being fully triggered.

What have others used successfully to switch the power to a load on and off using a BeagleBoard GPIO?

Any help appreciated.

Cheers,
     Chris MacGregor

2

I used a
International Rectifier
IRLML2060TRPBF
http://www.digikey.com/product-detail/en/IRLML2060TRPBF/IRLML2060TRPBFCT-ND/2271917
Digikey # IRLML2060TRPBFCT-ND

3

PS don't forget to account for the voltage drop across your FET, LEDS
and resistors

4

BS107A has too high Vgs(th). You need a mosfet with threshold voltage
lower than 1.7V. Digikey has a good parametric search. Select Vgs(th)
up to e.g. 1.5V and all other parameters that are important (like max.
dissipated power, max. Vds ) and pick one that will be most convenient
for you.

j.