Check the Vf of the LEDs you are using.cyborg5 wrote:We're also working on a 5 V system. My datasheet says that the maximum continuous collector current is 600 mA.
Yes, that is correct, the ~5-ohm resistor above. Although, it depends on the current capability of the 5V supply.cyborg5 wrote:I would need some sort of a current limiting resistor in line with that to keep the transistor current under specification.
Just like above, you have to subtract the Vf of the LED and the Vsat of the transistor. (5V - 1.5V - 0.6V = 2.9V, 2.9V/0.1A = 29-ohmcyborg5 wrote:at least a 50 ohm resistor given 5 V supply and a 100 mA maximum rating.
Not really. It has more to do with the base current and the transistor's gain. If the transistor can stay "fully saturated" and below it's power dissipation, then the "on resistance" will be nominal because it is related to the somewhat fixed Vsat voltage.cyborg5 wrote:Is there internal resistance in a fully saturated transistor that limits its current?
cyborg5 wrote:I thought it was just the minimum voltage necessary to turn on the LED.
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