Characteristics of P-N Junction Diode
A diode is the joining of two semiconductors, one a p-type semiconductor, the other an n-type. Their joining produces strange effects at their interface. The two semiconductors each have a terminal attached, allowing electricity to pass through like a regular resistor.
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Uni-directional Current
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The n-type semiconductor contains electron-donor atoms (n = "negative"); the p-type contains electron receivers. The interface between them sets up an electromotive force that prohibits current flow in one direction between the diode terminals.
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Unconventional Resistor
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Because resistance in a diode is therefore a function of the direction of the current, diodes don't obey Ohm's law like conventional resistors. The potential drop of a current across the diode plotted against the current is not straight like most resistors, but instead flat in one section and exponential in another.
DC Converter
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Because a current is allowed in only one direction, diodes are used as filters of alternating currents, allowing through only direct current. A DC-to-DC converter from 12V to 6V uses a diode, for instance.
Light Bulbs
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Without special coatings to modify it, a light-emitting diode (LED) emits light of a specific color. This is because electrons from the n-type semiconductor can fall into only one electron shell position of the p-type atoms, and therefore only one energy level.
Solar Energy
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Some n-type semiconductors give up electrons when struck by photons, such as from sunlight. The electromotive force at the semiconductors' interface then pushes the electrons in one direction. This gives rise to a DC current--the basis for photovoltaics.
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References
- Photo Credit "A healthy assortment of components" is Copyrighted by Flickr user: oskay (Windell Oskay) under the Creative Commons Attribution license.
