A diode is an electronic component with two electrodes (connectors). It allows electricity to go through it only in one direction.
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Diodes can be utilized to change over rotating current to coordinate current (Diode connect). They are regularly utilized in power supplies and here and there to disentangle abundancy regulation radio signs (like in a precious stone radio). Light-discharging diodes (LEDs) are a sort of diode that create 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 tubes. 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 Fleming valves are not used much anymore because they have been replaced by semiconductor diodes. Thomas Edison also discovered this property when working on his light bulbs.
Construction
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 it makes a good p-side semiconductor. Other chemicals can also work.
The connector to the n-side is called the cathode, the connector to the p-side is called the anode.
Function of a diode
Positive voltage at p-side
If you give positive voltage to the p-side and negative voltage to the n-side, the electrons in the n-side will want to go to the positive voltage at the p-side and the holes of the p-side will want to go to the negative voltage at the n-side. Because of this, current flow is able to exist, but it takes a certain amount of voltage to get this started (very small amount of voltage is not enough to get the electric current to flow). This is called the cut-in voltage. The cut-in voltage of a silicon diode is at about 0.7 V. A germanium diode needs a cut-in voltage at about 0.3 V.
Negative voltage at p-side
If you instead give negative voltage to the p-side and positive voltage to the n-side, the electrons of the n-side want to go to the positive voltage source instead of the other side of the diode. Same thing happens on the p-side. So, current will not flow between the two sides of the diode. Increasing the voltage will eventually force electric current to flow (this is the break-down voltage). Many diodes will be destroyed by a reverse flow but some are made that can survive it.
