Constant current source

Hello Ning,

Should the current always be 100mA (never off)?

Is there a headroom limitation? In other words, what is the output voltage if load is open (or too high of a resistance).

Is there an accuracy requirement? +/-5% for example.

Hello Ning,

Ron will be able to provide good advice here.  But if you would like to start out by seeing various ideas for how something like this might be implemented, you may be interested in figures 34 to 38 of our AN-31 Amplifier Circuit Collection.

Regards,

Daniel