I would recommend that the OP google for circuits using the LM317 voltage regulator.
No mention is made of the output voltage(s) or current, or what will power it, so all I can be is very generic.
Look up this device and see if you can find circuits to meet your (unspecified) requirements.
Chat_ghosty, that circuit will give you about 10mA and relies on a 1V reference (and I'm not sure were you'll get that -- another regulator?)