Originally Posted by
fulcrum
If you run them at 2-4 MHz you might be able to drive them at 0.1 to 0.15? A. The (pulse) energy output of each LED will be a lot lower then the output in the Blinder. My best guess is you will need around 100 LEDs with 50 or 100 driver circuits (Expensive MOSFET drivers). Try to get this small enough for a commercial product.
MOSFETs rated at a few hundred milliamps aren't that expensive, and in SMD form are small as well. MOSFET arrays could be used to drive a bank of LEDs. The challenge though is gate capacitance, which increases the switching time (and heat generation) of the MOSFET unless you can drive the gate with a lot of current.
Also, the LEDs can be run in series. A typical IR LED's forward voltage is around 1.6 volts @ 100 mA (looking at the Vishay datasheet posted earlier). So, a 5 volt circuit can drive 3 LEDs in series. Bump the voltage up to 12V and you can run 7 LEDs in series from one MOSFET.
The aforementioned LEDs have a rise and fall tim e of 30ns. So, at a 50% duty cycle the highest practical frequency would be 16 MHz. You could drive those LEDs at a 12.5% duty cycle at 4 MHz.
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