This switch is part of cheap light fixtures under my kitchen cupboards. I got them several years ago. One switch has gone bad and I've been trying to get it replaced for months, if not years. Suffice to say I just couldn't find any replacement that would…
Not really a constant current source. At least not really independent of supply voltage. With the addition of a Zener diode it could be improved a bit. A 2 transistor variant would be better. Or just buy an LM317 straight away.
The MCP1804 is quite a good regulator, very low standby consumption, smaller footprint too. So I switched to that and shrunk the board by 2mm. Can't make it much smaller without moving to insanely small parts.