What you are describing is a constant current switching driver. Not impossible but for a single 20mA LED is a bit pricey and they will be quite rare to get hold of.
I think this what you asking but on a smaller scale. With a current splitter you can make different Amperage amounts each led
I wonder why there are no self-contained switching circuits on a chip. Is it because the caps and inductors involved are just too big and put out too much heat or EM noise?
I wonder why there are no self-contained switching circuits on a chip.
Can you now?Never come across such a circuit, pray tell how this magic works. It is clear you know little about ohms law.