View source for Diodes

== Introduction ==
A [[Diode|diode]] is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate.

== History ==
The first types of diodes were vacuum tube devices, also known as thermionic diodes, invented in the early 20th century. The discovery of the [[Semiconductor|semiconductor]] properties of various materials in the mid-20th century led to the development of the modern diode.

== Types of Diodes ==
There are several types of diodes, each with its own specific function and characteristics. These include:

=== Semiconductor Diodes ===
[[Semiconductor Diode|Semiconductor diodes]], the most common type of diode, are composed of a piece of semiconductor material with a p–n junction connected to two electrical terminals.

=== Zener Diodes ===
[[Zener Diode|Zener diodes]] are used for voltage regulation, preventing circuits from exceeding a specific voltage.

=== Light Emitting Diodes ===
[[Light Emitting Diode|Light Emitting Diodes (LEDs)]] emit light when an electric current passes through them.

=== Photodiodes ===
[[Photodiode|Photodiodes]] are designed to be sensitive to light, and are often used in solar panels and light sensors.

=== Tunnel Diodes ===
[[Tunnel Diode|Tunnel diodes]] have a high forward resistance and are used in high-frequency applications.

== Diode Function ==
A diode’s main function is to allow an electric current to pass in one direction (called the diode’s forward direction), while blocking it in the opposite direction (the reverse direction).

== Diode Symbol and Polarity ==
The symbol of a diode is an arrow with a line at its head. The arrow represents the direction in which current is allowed to flow.

== Diode Characteristics ==
Diodes have two characteristics that define their operation: Forward voltage drop and Reverse recovery time.

== Diode Applications ==
Diodes are used in a wide variety of applications, including:

* Power conversion
* Over-voltage protection
* Logic gates
* Radio demodulation
* Ionizing radiation detectors

== Diode Testing ==
Testing a diode involves measuring the forward voltage drop and checking for a reverse leakage current.

== See Also ==
* [[Transistor]]
* [[Resistor]]
* [[Capacitor]]

[[Image:Detail-53223.jpg|thumb|center|A close-up image of a semiconductor diode.|class=only_on_mobile]]
[[Image:Detail-53224.jpg|thumb|center|A close-up image of a semiconductor diode.|class=only_on_desktop]]

[[Category:Electronics]]
[[Category:Semiconductors]]
[[Category:Electronic Components]]