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The History of Diodes
German physicist Ferdinand Braun, a 24-year old graduate of the University of Berlin, studied the characteristics of electrolytes and crystals that conduct electricity at Würzburg University in 1874. When he probed a galena crystal (lead sulfide) with the point of a thin metal wire, Braun noted that current flowed freely in one direction only. He had discovered the rectification effect at the point of contact between metals and certain crystal materials.
The first selenium diode was constructed in 1886 by C.E. Fitts but was not made practical until the 1930s.
Walter Schottky, in 1938 created a theory that explained the rectifying behaviour of a metal-semiconductor contact as dependent on a barrier layer at the surface of contact between the two materials. The metal semiconductor diodes later built on the basis of this theory are called Schottky barrier diodes.
The invention of the transistor is largely credited to Walter Brattain, John Bardeen, and William Shockley. But, like most great inventions, the transistor was a milestone in a creative process that involved many people. One of those people was Russell Ohl, who, in 1940 stumbled on the semiconductor “p-n” junction diode, the device that Bardeendescribed as fundamental to the work of the team that built the transistor.
In 1955, Rubin Braunstein reported infrared emission from gallium arsenide, however James R. Biard and Gary Pittman of Texas Instruments presented the first IR lamp (PDF) in 1961 which was the first practical LED to be patentedin the August of the same year. Consequently, the first commercial LED was an IR LED with 890 nm light output and was called the SNX-100.
A diode only allows current to flow in one direction.
Electrical current flows from the cathode side of a diode to the anode side. Generally the cathode side is connected to the negative side of a DC power supply. A diode has a black band marking the cathode side.
Diodes typically require a minimum amount of voltage for the current to flow through them.
Some of the major types of diodes include light-emitting diodes (LEDs), Zener diodes, small signal diodes, power rectifiers, and photodiodes.
Diodes were originally known as rectifiers. Today one type of diode, known as the power rectifier, is used to make power supplies for electronics.
A Zener diode, invented by Melvin Zener, is a special diode that is used as a voltage regulator. It can allow current to flow in both directions when enough voltage is present.
A small signal diode can perform a number of functions such as detections of radio waves and conversion of low current AC to DC.
Reference: Silicon Engine
Engineering & Technology History
Science with Kids