Short version: can I use this MOSFET http://www.irf.com/product-info/datasheets/data/irlml2246pbf.pdf
to drive a 2.4A load @ 5V with 0.1ms pulses from the output of a 74ac138 decoder? Do I need a resistor between the 74ac138 pin and the MOSFET gate? If so, what value?
Long version: I have a 24x16 LED matrix I'm trying to drive as bright as possible (each LED @ 100mA for 0.1ms). The columns are controlled by TLC5916 constant current drivers connected to the cathodes; the row anodes by a pair of 74ac138 3:8 decoders.
I've tried a couple of PNP transistors but the only way I can get enough current out of them is by pulling 50mA out of the 74ac138 pins, which is at the max threshold so probably not the best idea. With the latest transistors (http://www.diodes.com/datasheets/ds31149.pdf
) and 150 ohm resistors (so Ib=24mA) I'm only getting about 1.6A out.
Based on dc42's excellent explanation in another thread (http://arduino.cc/forum/index.php/topic,76363.msg577560.html
) I think I'm not able to drive the transistors to saturation, which would explain the lack of power to the LEDs and the heat the transistors are generating.
So now I'm going to try some logic level P-channel MOSFETs. They need to be surface mount for due to circuit board limitation size, and I'm trying to save money because I need 16 of them and these are the least expensive ones I can find.
Will this MOSFET work? If not, can you give me any pointers on what I missed?
As always, thanks to everyone for your continued assistance.