Facts on Diodes
A diode is an electronic device that consists of two electrodes, or conductors of electrical current, where one subatomic particle has a negative charge and only flows in one direction. Since a diode can control the flow of electrons, it is considered a rectifier, which is a device that converts alternating current into direct current. There are several types of diodes used in electronic devices.
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Light Emitting Diodes
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The most common type of diode is a light emitting diode (LED). These diodes can be produced in a variety of colors or across different wavelengths. LEDs are used in applications as a low-energy source, and in devices where it is necessary to use a light that is small in size. Devices where LED lights are include Christmas tree lights, automobile brake lamps, TVs, street lamps, wall lamps, chandeliers and video games.
Photodiodes
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After light hits a positive-negative semiconductor diode the light may excite electrons, and the result is a transfer of energy. Because of this, some diodes such as photodiodes are used to detect light. These are different from photo detectors because in addition to detecting light, they make use of the current it creates. Examples photodiode applications include clock radios with dimming displays, and receivers for remote controls in VCRs and some televisions.
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Laser Diodes
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Laser diodes are powered lasers that produce coherent light, which is the distinguishing factor from other light emitting diodes. The contacts on these diodes are semiconductors, with one contact carrying a positive charge and the other a negative charge. Laser diodes are used in products like CD players, DVD players and Blue-ray devices. Other applications include laser printing, barcode reading, image scanning and laser surgery.
Cat's Whisker Diodes
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The cat's whisker diode's name is derived from the device's thin wire that connects to the semiconductor silicon contact and creates a metal-to-semiconductor diode. This is one of the oldest types of diodes and is found in crystal radios and some other types of radio transmitters. The connection is unstable, but it is adequate enough to transmit a basic radio signal.
Point Contact Diodes
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A point contact diode operates similarly to a cat's whisker diode in that it contains a contact that is made from a semiconductor where a small metal wire is barely touched. The wire functions as the other contact, and a current flows through the wire to the semiconductor. This type of diode is not really useful except for in basic radio frequency applications.
PIN Diodes
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PIN diodes are similar to photodiodes. These diodes have a positive silicon conductor on one end and a negative type semiconductor on the other end. The letter "I" in PIN stands for intrinsic, because the material located between the positive and negative conductors is an intrinsic conductor. These diodes are commonly used in radio switches, but do not have many uses outside of this purpose.
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