The simplest kind of semiconductor is a diode. A diode is only one type of semiconductor. By combining several kinds of semiconductor material. A diode is made of one layer of P-type semiconductor and one of N-type semiconductor. Diodes allow current flow in only one direction.
On a schematic, the triangle in the diode symbol points in the direction that current is permitted to flow by using conventional current flow theory.
Diodes are used for many purposes in electrical circuits. These purposes include illumination, rectification, and voltage spike protection.
The following diodes are used in electrical circuits:
1. Voltage regulation (using Zener diodes)
2. Indicators (using LEDs)
3. Rectification (changing AC current to DC current. A common application would be a battery charger.)
4. Clamping to control voltage spikes and surges that could damage solid state circuits (acting as a circuit protector)
5. Photo sensing switch ( Photo diodes)