Voltage and Current Sources

For the operation of all the electrical/electronic circuits a source of power/energy is essential. These sources are classified into two categories as:

(i) Voltage Sources  (ii) Current Sources

The voltage and current sources can be further classified as dependent sources and independent sources.

Independent Voltage Sources:

In the independent voltage source, the terminal voltage of the source is not dependent on any other voltage source or current source. The independent voltage sources can be further classified as:
(i) Ideal voltage sources   (ii) Practical voltage sources

Time invariant sources: The time invariant voltage source is the source whose terminal voltage does not change with time. That means it is a D.C. voltage source.

Time variant sources: The terminal voltage of these sources changes with time. So they are basically the ac voltage.

Independent Current Sources:

For an independent current source, the current supplied by the source does not depend on any other voltage source or current source. The independent current sources are further classified as:
(i) Ideal current sources  (ii) Practical current sources

Time invariant current source: The output current of this source does not change with time. So basically this is a dc current source.

Time variant current source: The output current of this source changes with time. So basically it is an ac source.

Dependent Sources:

The dependent voltage sources or dependent current sources will produce terminal voltage or current that is dependent on some other voltage or current in the same circuit.

Voltage Dependent Voltage Source (VDVS): This is a voltage source which produces a terminal voltage V which is dependent on some other voltage V' produced in the same circuit. Hence, V = kV'.

Current Dependent Voltage Source (CDVS): This is a voltage source which produces a terminal voltage V which is dependent on current I' produced in the same circuit. Hence, V = kI'.

Voltage Dependent Current Source (VDCS): This is a current source which produces a current which is dependent on voltage V' produced in the same circuit. Hence, I = kV'.

Current Dependent Current Source (CDCS): This is a current source which produces an output current I which is dependent on some other current I' produced in the same circuit. Hence, I = kI'.