Why exactly do laser diodes need drivers? Why do LEDs just need resistors?

My understanding is that they're very similar to regular LEDs, but LEDs only need a resistor.
What makes laser diodes so special?
Are there circumstances under which laser diodes don't need a full driver circuit?

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Lasers DIODES are LED like structures. They are run in a critical way though that means that as little as 20% more voltage will destroy them, and similarly for current.

It is critically important for a laser diode driver to protect the diode from over-voltage, like even very fast noise spikes, to stop the diode failing prematurely.

jonrb (author)  steveastrouk2 years ago

Does that mean that using a capacitor to smooth any spikes would be insufficient?

Yes, unless you know exactly where to put them. Are you using this diode in a "DC" situation, or are you intending to modulate it ? If you're just running it DC, its a lot easier to be safe. Even a classic LM317 in constant current mode could be used then.

rickharris2 years ago

I am going to go nuts soon - I penned a fairly long response to this question which has subsequently disappeared.

Have a look here


It may help you understand how these things work.

Lasers and LEDs work differently.

LEDs will work high voltage ranges like 3 to 70 volts and low current like 5 ma.

Lasers diodes are more like 3.5 volts and 150 ma and more.

So LEDs just need a resistor to limit the current and laser diodes need a driver to push the right current.