In article , jasen
wrote:

On 2006-09-29, Al wrote:

If your LED is specified at 10mA, then get two diodes whose forward
voltage is 0.75V at 10ma. Put them in series with your LED. If the
supply voltage goes up and the current goes up, the forward voltage of
the diodes will go up also thereby dropping more voltage across them.

yeah, if the current doubles the voltage may increase maybe 10%
how's that going to help?

Thus the dynamic resistance of the dropping diodes serves as a voltage
regulator. Really good diodes with a low dynamic resistance won't do.

it seems to me that regular resistors would work better,

If your current doubled for some reason, you have other big problems.

Al