|MadSci Network: Engineering|
A constant current source is usually created by monitoring the voltage drop across a resistor and keeping that voltage constant. You can do this with OP amps. You can also obtain 3 terminal parts called current mirrors. The current through one input of the current mirror is a multiple of the current through the other side. Quite a bit of the decision to design a particular constant current source is based on the amount of current you want to deliver. I can answer more fully if you give me more details. Gus
Try the links in the MadSci Library for more information on Engineering.