I need advice for a power transistor
August 22, 2011
Since DanM posted his laser blog I was hooked to the idea of pulse driving laser diodes.
I have created my own pulsing hardware using an ATMega328 to generate a 62.5 ns pulse at 16 Mhz, driving the diode trough an ULN2803 (Toshiba made) which seems to be able to respond well to such short pulses.
However the ULN2803 is limited in power output so the highest current I could sink is about 700mA (I know the ULN2803 is limited to 500mA yes) by parralelling outputs. At this level the ULN2803 is way over its limits and starts overheating.
So to proceed with higher currents (I'm positive the diode can take at least 1A in pulsed mode) I'm looking for a NPN transistor with at least 1A/12V rating, faster then 60 ns on/off switching times which can be driven with 5V TTL logic .
Has anyone suggestions? I'm sure there are lots of options out there but I have a hard time finding the "right" one, I need an expert :)
Later edit: Thank you all for the input, I'm settling on a MOSFET, I'm sure I can locate some in the electronic junk I have at home to do some testing. If the laser diode still holds up at 1 A I'll mount it on the Phoenix - see if cutting is possible which such a low power diode in pulsed mode :D