Diode
Introduction
A diode is a specialized electronic component with two electrodes called the anode and the cathode. Most diodes are made with semiconductor materials such as silicon, germanium, or selenium. The fundamental property of a diode is its tendency to conduct electric current in only one direction.
History
The first types of diodes were vacuum tube devices, also known as thermionic diodes, invented in the early 20th century by John Ambrose Fleming, based on observations by Thomas Edison. The vacuum tube diode, which is now largely obsolete, was used in early radio and telephony as a detector and rectifier.
Operation
When a diode is in forward bias condition (anode is positive with respect to the cathode), it conducts current easily. However, when the diode is in reverse bias (anode is negative with respect to the cathode), it resists current flow. This unidirectional behavior is called rectification.
Types of Diodes
There are several types of diodes, each designed for specific applications. These include:
Semiconductor Diodes
A semiconductor diode, the most common type, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.
Zener Diodes
Zener diodes can allow current to flow from its anode to its cathode like a normal diode, but it can also flow in the reverse direction when its "Zener voltage" is reached.
Light Emitting Diodes
Light Emitting Diodes (LEDs) emit light when an electric current passes through them. They are used in a wide range of applications from lighting to data communication.
Photodiodes
Photodiodes are designed to be sensitive to light. They can be used in solar cells, in photometry, or in optical communications.
Schottky Diodes
Schottky diodes, named after the German physicist Walter H. Schottky, are diodes with a low forward voltage drop and a very fast switching action.
Applications
Diodes have many applications in electronics, some of which include:
- Voltage regulation (Zener diodes)
- Radio demodulation (detector diodes)
- Power conversion (rectifier diodes)
- Over-voltage protection (TVS diodes)
- Logic gates (diode logic)