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Why do LEDs have a maximum current?

up vote 14 down vote favorite

So I understand that LED's have a maximum current (like 20mA for instance), but scientifically why is this?

Using the water analogy it seems like a high voltage would be the thing that would mess up something (I like to think of it like a huge amount of "pressure" blowing out a pipe or something). Why would a rate of electron flow damage something?

2 Answers

up vote 4 down vote accept

There's a forward voltage drop of a couple volts across the LED. This Voltage drop times the Current is the Power dissipated in the device. It creates light, but also heat. It's the heat that kills the LED.

up vote 3 down vote

All nice answers. I just wanted to add that if there was no non-radiative recombination in the LED's, then there would be much less heat and one could push more current through before it heats up... (Think newer high efficiency LED's)


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Why do LEDs have a maximum current?

up vote 14 down vote

So I understand that LED's have a maximum current (like 20mA for instance), but scientifically why is this?

Using the water analogy it seems like a high voltage would be the thing that would mess up something (I like to think of it like a huge amount of "pressure" blowing out a pipe or something). Why would a rate of electron flow damage something?


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up vote 9 down vote

There's a forward voltage drop of a couple volts across the LED. This Voltage drop times the Current is the Power dissipated in the device. It creates light, but also heat. It's the heat that kills the LED.

edit

If you drop a standard LED across a voltage source while holding it by the head, it sometimes generates enough heat before it dies to get noticeably warm. Don't do this with a high-power LED! - Warren Young Jan 4 at 13:43

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