I need to create an adjustable DC power supply that can output between 0.1 and 0.75V DC at 300 mA (possibly as little as 100 mA). My input voltage can be anything, including +/- rail.
Currently I am using an adjustable bench top power supply to supply this voltage, but I need to package this in a smaller enclosure. Once adjusted via trim pot the voltage won't change, and I do need as stable a DC source as possible (both temperature and voltage stability). Long story, but this DC power is being injected into an RF signal via a "Bias T" so an RF sin wave can be "converted" into a digital signal (-0.5V to 0.5V pk-pk becomes 0-1V and interpreted as PECL digital input. Ugly but it works!).
Anyway, all of the usual LDO / regulators / step down convertors appear to cease working at ~0.5 or 0.75V and I most likely need approximately 0.35V. Everything shares a common ground so I cannot use a floating ground for this application (i.e. 1V and 1.35V power supplies).
I am considering a unity op-amp where I set the input V+ using a trim pot. However, I can't seem to find an op-amp that provides enough mA (voltage following op-amps; I'm not familiar with current op-amps to know if that would work). Does anyone have any suggestions here? I'm somewhat at a loss.