# How does a voltage independent current source work?

So I'm having some trouble understanding what a voltage independent current source is. How can you have a current without a voltage. as I understand it voltage or EMF is the force that drives the electrons to move, thus making a current.

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–  Qmechanic May 6 '12 at 11:30
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## 1 Answer

A current source is a device that will (ideally) provide a constant pre-specified current to the connected load no matter what the load's resistance is, so that it will adjust the voltage across its terminals to get the current right (instead of the other way around as in a(n ideal) voltage source).

Of course, this is only ever approximately possible, and the quality of that approximation will depend (as with voltage sources!) on how much is known or expected about the load resistance and how fancy the device is -- see for example wikipedia.

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Correct, nothing to add. +1 –  Pygmalion May 6 '12 at 15:44
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