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What is the Difference Between Diodes, Anodes and Cathodes?

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  • Written By: M. McGee
  • Edited By: Lauren Fritsky
  • Last Modified Date: 17 September 2016
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A semiconductive diode is a basic component of a huge number of electrical systems. These components have two terminals—one that takes in electricity and one that lets it out. This process works in one way; if a terminal takes in electricity, it doesn’t let power back through. The cathode is the part of a diode that allows power to flow out, and an anode is the part that allows it to flow in. It is the combination of these two elements that allows the diode to function.

The physical construction of a diode varies slightly based on the reason for its use, but certain factors remain the same. The diode has two terminals, a cathode and an anode, that are connected by a small amount of semiconductive material. This material is typically silicon, but a wide range of different materials may be used. The entire assembly is surrounded in a glass or plastic covering. Diodes may be any size, and while most diodes aren’t very big, they can be almost microscopically small.

The anode takes in electricity. This terminal gets its name from the negatively charged anions that move towards it during a common electrochemical reaction. The charge of the anode varies based on the device’s function. If the device uses power, the charge is negative, and if it makes power, its charge is positive. This polarity shift allows electricity to flow properly from the terminal.

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A cathode is essentially the opposite of an anode. The cathode allows power to flow out of the device. This terminal gets its name from the positive-charged cathodes that it attracts during a reaction. When a device uses power, the cathode is positive, and it is negative when it generates power.

The material in the middle of a diode is a semiconductor. Semiconductors are materials that don’t conduct electricity like a standard conductor, but don’t prevent it like an insulator. These materials fit in between and have very specific properties when electricity flows through them. The majority of mass-produced diodes use a silicon semiconductor, but ones made of germanium are not uncommon.

Since their invention in the late 1800s, basic diodes haven’t changed very much. The materials used to make them have improved, and the basic design has become a lot smaller, but that is really all that has changed. Neither the principles to make them nor their design is much different from the original creation.

The biggest innovation with diodes is in the alternate versions the initial invention inspired. There are dozens of different types of diodes that all work slightly differently. These different diodes have all sorts of additional functions beyond the in-out methods of the basic form. They range from the tunnel diode that operates on a quantum scale to the light-emitting diode (LED) used as a light source in many modern electronics.

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