Types of Diodes

LED is also a type of diode & emits light when an electric current passes through it.

Thermionic Diodes

Thermionic diodes are vacuum tubes, which are nothing but electrodes surrounded by a vacuum within a glass envelope similar in appearance to incandescent light bulbs.

Semiconductors diodes

Presently many diodes are based on semiconductor p-n junctions. In a p-n diode, conventional current can flow from the p-type side (or the anode) to the n-type side (that is the cathode), but cannot flow in the opposite direction. Another type of semiconductor diode, the Scotty diode, is formed by the contact between a metal and a semiconductor rather than by a p-n junction.

Zener Diodes

Diodes that can be made to conduct backwards. This effect we call it a  Zener breakdown, which occurs at a accurately defined voltage, allowing the diode to be used as a precision voltage reference. The minimum voltage available is 2.4V. Mostly Power ratings of 400mW and 1.3W..

Photo Diodes

Used in Solar cells and in photometry.

LED's Light Emitting Diodes