What is a current source?

Answer 1

A current source is a source that we can draw current from and can regulate to control the amount of current we draw. It is kind of a "mirror" of the voltage source. Here's how it might work. We usually are interested in keeping the current constant when we use a current source (though not always). To do this takes a varying voltage source to keep that current constant when using the source with a dynamic load (a load that is changing). There will have to be a way for the source to sense current flow and compare it to the setting put in. That way the source can maintain that constant current by adjusting to the correct voltage needed to maintain it. Many battery charging applications require this technology. We want "maximum" current so we can quickly charge the battery, but we cannot "overload" the battery, so we have to be careful not to do that. A constant current source is the answer. It will supply a steady "maximum" current, and the source will (as the battery charges and the "resistance to more charge" increases) increase in voltage to keep that amount of current flowing into the battery to charge it in the shortest time. A VERY GOOD EXPLANATION and I could add that a perfect current source would have 0 (zero) input/output impedance or you could say it's would be more like "a short that provides power".