I need a rather unusual power supply for a very different purpose. I need an output of 5mV to 50mV to power a incandescent lamp to measure it's cold resistance. You know, for precision cold resistance measurement it must be power up by very low voltages so that the filament heats up very very little, so that it becomes negligible. I'm using a 6V lamp (or a 12V automotive lamp), which starts to glow faintly at 400mV, so 5-50mV might be good for cold resistance. I'll use MAX4372 as a CSA.
In next step, I'll need a not-so-precision power supply (may be separate from the previous one) to power up the lamp upto 12V. I used PWM+Power transistor for this purpose. But I realised that there was a problem. As the current flows through the filament and it heats up, the resistances decreases, and the voltage increases slowly. So, the voltage is never stable, increases about 40mV per half minute!
So, I need to replace the whole concept. A LM317 + digital potentiometer may be used, I think. But LM317 Vref is 1.25V, so getting down to 0 volt is not easily possible. Any alternative option for LM317, Which can deliver down to 0V. Any other suggestion for the purpose?