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Many circuits operate LEDs at less than the specified maximum current to save power, or to reduce brightness, or to use a common resistor value. For indoor use, tiny surface mount high-efficiency LEDs can easily light up with 1 mA (0.001 A) or more current, which most digital logic outputs can easily source or sink.
LED power dissipation is modeled as a current source; thermal resistance is modeled as a resistor; and the ambient temperature is modeled as a voltage source. High power light-emitting diodes (LEDs) can use 350 milliwatts or more in a single LED. Most of the electricity in an LED becomes heat rather than light – about 70% heat and 30% light. [1]
Efficiency: LEDs emit more lumens per watt than incandescent light bulbs. [63] The efficiency of LED lighting fixtures is not affected by shape and size, unlike fluorescent light bulbs or tubes. Size: LEDs can be very small (smaller than 2 mm 2 [64]) and are easily attached to printed circuit boards.
A LED is a long-lived light source, but certain mechanisms can cause slow loss of efficiency of the device or sudden failure. The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide , and others , with various trace doping elements , are used to produce different ...
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
Several "extra-bright" sets also use 70 or 105 bulbs, keeping the per-bulb voltage at 3.5 instead of 2.5. LED sets can vary greatly. Common is a set of 60 (2 volts per bulb), but white LED sets use two circuits of 30 (4 volts per bulb).
Reported in the January 5, 2004 issue of the journal Applied Physics Letters, Milton Feng and Nick Holonyak, [1] the inventor of the first practical light-emitting diode (LED) and the first semiconductor laser to operate in the visible spectrum, made the world's first light-emitting transistor.
A small resistor may also be contained in the base of older two-volt LED colors (red, orange, yellow) when in a mixed-color set, so that they match the three volts needed by the newer colors (blue, deep green, purple, white), however other manufacturers only change the value of the resistor that is a part of the cord set itself.
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