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LEDs as a low noise shunt regulator?

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EE54:
Hi everyone, recently I came across this Reddit post: https://www.reddit.com/r/electronics/comments/ro9h5b/voltage_regulator_from_1_led/
In it, someone in the comments claims that an LED offers better noise performance ( but worse regulation) than a zener diode when used as a shunt voltage regulator.

How true is this?
Has anyone tested this before?

RoGeorge:
I didn't measured that, but it could be true.

Zener diodes are reverse polarized, working in some sort of a controlled breakdown, similar with a continuous avalanche, while a LED is direct polarized, so no avalanche noise from the LED.

SeanB:
They do make reasonable voltage references, but have a high slope resistance, and are very light sensitive as well. But if you want a simple low voltage reference that is better than 2 or 3 silicon diodes in forward bias, they do work well enough. In non critical applications they do work well enough, but do not expect them to replace a reference voltage IC at all, though they are rather better than low voltage zener diodes.

I have used them as voltage references, but varying the current from 100uA to 1mA increased forward voltage drop by around 0.2V for a red 5mm LED, and going to 10mA was about the same again. If exposed to ambient light they will have additional noise from the light hitting them as well, making them useful as a light sensor on a MCU pin, as both ambient light sensor and power indicator. Just turn off every minute for 2ms, and sample the pin voltage with the ADC with a weak pull down, or 10k parallel resistor, then turn it back to an output and turn it high, so the high output drives the LED again, via a 1k series resistor.

2N3055:
Google this : "walt jung led regulator"

EE54:
Thanks, that was quite an interesting read. Never knew you could use LED for that.

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