What is Diode?
[[File:1N4001 Diode.jpg|thumb|Diode]] [[File:Diode 3D and ckt.png|thumb|Anode and Cathode. Cathode is marked on the case.]] A '''diode''' is an [[electronic component]] with two [[electrode]]s (connectors) that allows [[electricity]] to go through it in one direction and not the other direction. Diodes can be used to turn [[alternating current]] into [[direct current]] ([[Diode bridge]]). They are used in power supplies and sometimes to decode [[amplitude modulation]] radio signals (like in a [[crystal radio]]). Light-emitting diodes ([[LED]]s) are a type of diode that produce light. Today, the most common diodes are made from [[semiconductor]] materials such as [[silicon]] or sometimes [[germanium]]. == History == The first types of diodes were called Fleming valves. They were [[vacuum tube]]s. They were inside a glass tube (much like a [[lightbulb]]). Inside the glass bulb there was a small metal wire and a large metal plate. The small metal wire would heat up and emit electricity, which was captured by the plate. The large metal plate was not heated, so electricity could go in one direction through the tube but not in the other direction. Fleming valves are not used much anymore because they have been replaced by semiconductor diodes, which are smaller than Fleming valves. [[Thomas Edison]] also discovered this property when working on his light bulbs. == Construction == [[File:Diode tube schematic.svg|thumb|upright|Structure of a tube diode]] Semiconductor diodes are made of two types of semiconductors connected to each other. One type has atoms with extra electrons (called the n-side). The other type has atoms that want electrons (called the p-side). Because of this, the electricity will flow easily from the side with too many electrons to the side with too few. However, electricity will not flow easily in the reverse direction. These different types are made by [[doping (semiconductor)]]. Silicon with arsenic dissolved in it makes a good n-side semiconductor, while silicon with aluminum dissolved in i