Quote:
Originally Posted by j.p.s
Do 4 lead, three die (R, G, B) LEDs count as white? They have been around for quite a while.
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No they are not really white illumination. Just any colour of indicator, including the same illusion of white as any display screen.
Quote:
Originally Posted by jbjb
I'd say that counts as 3 LEDs packaged together, not a single LED. The multiple quantum well white LEDs on the other hand are genuinely monolithic - grown on a single substrate.
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There are no white LEDs. Just nearly monochrome with phosphors. Blue, Violet or UV.
The filament stick LED lamps have maybe 22 LEDs (minimum) in series on sapphire rod coated in mostly yellow phosphor. Shine UV or a bright blue LED in the dark on one that's off.
Some have better colour rendition by adding a second or third phosphor and even interspersing some other colours of LED. They are more efficient and longer life.
* Each stick might be about 55 V, so the power supply is more efficient than smaller number of chips in a spot lamp etc.
* The LED temperature is lower due to many more chips, so phosphor lasts better.
* The LED temperature is lower due to design and cooling gas fill.
* The light level per sq mm of phosphor is lower so phosphor lasts better.
They also give a more omnidirectional light.