Every electronic circuit requires some source of energy for its operation. The electrical energy may be supplied either in the form of a voltage or current. The electrical device which supplies the electrical energy required for the operation of an electronic circuit is known as a source.
Types of sources :
The sources required for the electronic circuits are of the following two types:
- Current source
- Voltage source
All the voltage and current sources may be classified into two categories are,
- Alternating current (A.C.)
- Direct current (D.C.)
Internal resistance of source :
All sources of electrical energy, either voltage or current have some internal resistance and value of resistance in ohm. The internal resistance of a source may be due to the following reason.
- The resistance of an electrolyte between the electrodes in the case of dry cell.
- The resistance of an armature winding in the case of D.C. generator or an alternator.
- The output resistance of an active device like a transistor in case of capacitor, signal generator or regulated D.C. supply.
The D.C. resistance offered by a source is known as an internal resistance.