A current source is an electrical device or circuit that provides a constant current to a load, regardless of the voltage across it, within its operational limits. It is the dual of a voltage source, where the current remains fixed while the voltage may vary depending on the load.
Key Features of a Current Source:
- Constant Current:
- Delivers a steady current, independent of changes in load resistance or voltage.
- Types:
- Ideal Current Source: Provides an exact and unchanging current, irrespective of load or voltage. (Theoretical concept.)
- Practical Current Source: Provides nearly constant current with slight variations due to internal limitations.
- Symbol:
- Represented as a circle or diamond with an arrow inside, indicating the direction of current flow.
Types of Current Sources:
- Independent Current Source:
- Provides a fixed current value, not controlled by any external signal.
- Dependent (Controlled) Current Source:
- The output current depends on an external input signal, such as voltage or current.
Applications:
- Biasing transistors in analog circuits.
- Simulating ideal current sources in circuit analysis.
- Powering LED arrays and lasers.
- Use in constant-current charging systems.
Current sources are fundamental in electronic circuits, especially in precision and analog applications, where stable current delivery is required.