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In circuit theory, an ideal current source is a circuit element where the current through it is independent of the voltage across it.

It is a mathematical model, which real devices can only approach in performance.

If the current through an ideal current source can be specified independently of any other variable in a circuit, it is called an independent current source.

Conversely, if the current through an ideal current source is determined by some other voltage or current in a circuit, it is called a dependent or controlled current source.

Symbols for these sources are shown in Figure 2.