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Why do some LED's produce more light than others at the same voltage/current?


Jonathan Kirwan

Jan 1, 1970
I ordered some LED's from to mess around with, but I
have a question:

This one says it produces 3000mcd at 3.5V forward voltage 20ma:

The one says it produces 18000mcd at 3.5V forward voltage 20ma:

Both have 30 degree viewing angles. Is the 18000mcd that much more


Interesting question. Since they are both GaN types, I would tend to
guess that it is more about the phosphors used and the resulting
distribution of the energy working with the human eye's sensitivities
that lead to the bulk of the differences. Or else about the viewing
angles (which you snipped in the bud.) Finally, it might be due to a
backside reflector of some kind in the brighter one.

It would be hard to believe that a factor of 6 in efficiency would
occur on GaN processing alone.

Looks like those two data sheets were dead copies of each other except
for the difference in mcd and part number. Perhaps Don K. will teach
us about what is going on here...