LYCOS RETRIEVER 
Light-Emitting Diode
built 636 days ago
The first known report of a light-emitting solid-state diode was made in 1907 by the British experimenter H. J. Round. However, no practical use was made of the discovery for several decades. Independently, Oleg Vladimirovich Losev published "Luminous carborundum [silicon carbide] detector and detection with crystals" in the Russian journal
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Because the voltage versus current characteristics of an LED are much like any diode, they can be destroyed by connecting them to a voltage source much higher than their turn on voltage. A good LED driver circuit is either a constant current source or an approximation to a current source made by connecting the LED in series with a current limiting resistor to a voltage source. The voltage drop across a forward biased LED increases as the amount of light emitted increases because of the optical power being radiated. One consequence is that LEDs of the same type can be readily operated in parallel. The turn-on voltage of an LED is a function of the color, a higher forward drop is associated with emitting higher energy (bluer) photons. The reverse voltage that most LEDs can sustain without damage is usually only a few volts.
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Truck-Lite uses LED technology for its Signal-Stat line, which now features more than 40 high-diode-count lamps, as well as its Super 80 LED interior trailer lamps. “Providing an economical LED lamp that meets or exceeds heavy-duty standards is critical in today’s market,” said Brad VanRiper, Truck-Lite’s senior vp & chief technology officer.
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An LED works in a similar fashion to the pn-junction diode electrically, though the first LED was created as a Schottky-like diode with a rectifying contact on carborundum (SiC) by H.L. Round in 1907. He applied up to 110V to crystals and noted orange to blue electroluminescence (Ref. 40).
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F[I]gure 2a shows the behavior of an LED, and Figure 2b shows the behavior of a laser diode. The plots show the relative amount of light output versus electrical drive current. The LED outputs light that is approximately linear with the drive current. Nearly all LEDs exhibit a “droop” in the curve as shown in Figure 2b. This nonlinearity in the LED limits its usefulness in analog applications.
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Headquartered in San Jose, California, Lumileds is the world's leading manufacturer of high-power LEDs (light-emitting diodes). When Lumileds was founded they needed to rapidly move their financial data into an independent business module. Tags: Oracle Corp., J.D. Edwards & Co., Cost Reduction, Light-emitting Diode, Supply Chain Management (SCM), Engineering, Manufacturing, Enterprise Software, Software Case studies
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Light-Emitting Diode