Current source

Ohms law current source (white background)

Voltage Source

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Current Source

Voltage Source (Controlled)

Current Source (Controlled)

Current source is an electrical component or 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 ideal current source delivers a constant current, as it has infinite internal resistance, so the voltage can change across its terminals without affecting the current it delivers. However, real-world current sources have non-infinite internal resistance, and their behavior only approximates that of an ideal current source within certain limits.

Types of Current Sources

There are two main types of current sources in electronics:

1. Independent Current Sources: These sources provide a constant current that does not depend on any other electrical quantity in the circuit. An example of an independent current source is a battery combined with a current-regulating circuit.

2. Dependent or Controlled Current Sources: These sources deliver a current that is dependent on some other voltage or current in the circuit. There are four types of dependent current sources:

  * Voltage-Controlled Current Source (VCCS)
  * Current-Controlled Current Source (CCCS)
  * Voltage-Controlled Voltage Source (VCVS)
  * Current-Controlled Voltage Source (CCVS)

Applications

Current sources have a wide range of applications in electronic circuits. They are used in:

• Biasing of transistors in amplifiers
• Active filters
• Current mirrors, which are fundamental building blocks in analog integrated circuits
• Charge pumps for generating higher voltages in circuits
• LED drivers, to provide a constant current to ensure consistent brightness

Design

Designing a practical current source involves various components like transistors, resistors, and sometimes operational amplifiers to achieve the desired current regulation. The design aims to maintain a constant current output despite changes in load resistance or supply voltage.

Limitations

Real current sources have limitations, including a finite output impedance, which affects their ability to maintain a constant current under varying load conditions. Additionally, their performance is influenced by temperature changes and the characteristics of the components used in the circuit.

Mathematical Representation

The behavior of an ideal current source can be described by Ohm's Law, where \(I = \frac{V}{R}\). For an ideal current source, \(I\) remains constant regardless of \(V\) or \(R\).

See Also

• Voltage source
• Ohm's Law
• Electrical resistance
• Electrical impedance
• Operational amplifier