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Simple Definitions

The most important electronics terms, demystified in one place.

Current source

Our Take

A current source is a power source that provides a set amount of current no matter what voltage is required to maintain the current. An ideal current source can create an infinite voltage but in reality, the voltage will be limited by the source. While less common than voltage sources, current sources are used in driving LEDs, charging batteries, and in semiconductor circuit design. Do not open-circuit current-sources as they will attempt to create an infinite voltage to overcome that open-circuit.

Book Definition

Supplies I = V/ri to load with ri in parallel.

Grob’s Basic Electronics, 11th Edition by Mitchel E. Schultz


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 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 resistive 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.

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