I've been looking at all sorts of voltage regulators to suit my needs, I'm arranging an adjustable voltage regulator in such a way that I'm actually using it as a precision current source. Turns out I can't paste an image, but you can see the "Precision Current Limiter Circuit" on pg12 of the LM317 datasheet here: http://www.ti.com/lit/ds/symlink/lm317.pdf
The idea is that there is a fixed voltage (enforced by the regulator) between the adjustable pin and the output pin. A resistor between those two nodes determines the output current.
My question is this: Is there an adjustable voltage regulator I can use at this setting for an output current of ~150uA? I haven't been able to find one that operates in this way below about 2mA. This is the only way I know of to make a precision current regulator.
EDIT: here is a good image of a voltage regulator being used as a precision current source: http://diyaudioprojects.com/Technical/Current-Regulator/1-Amp-Current-Regulator-Scheamtic.png.
This is what I am trying to achieve but the voltage regulators don't operate as intended at such low current and so I haven't been able to achieve a regulated current regardless of the load.