电流源，即理想电流源，是从实际电源抽象出来的一种模型，其端钮总能向外提供一定的电流而不论其两端的电压为多少，电流源具有两个基本的性质：第一，它提供的电流是定值I或是一定的时间函数I(t)与两端的电压无关。第二，电流源自身电流是确定的，而它两端的电压是任意的。

由于内阻等多方面的原因，理想电流源在真实世界是不存在的，但这样一个模型对于电路分析是十分有价值的。实际上，如果一个电流源在电压变化时，电流的波动不明显，我们通常就假定它是一个理想电流源。

像光电池一类的器件，工作时的特性比较接近电流源。

A current source is an electronic circuit that delivers or absorbs an electric current which is independent of the voltage across it.

A current source is the dual of a voltage source. The term, constant-current sink, is sometimes used for sources fed from a negative voltage supply. Figure 1 shows the schematic symbol for an ideal current source, driving a resistor load. There are two types. An independent current source (or sink) delivers a constant current. A dependent current source delivers a current which is proportional to some other voltage or current in the circuit.