There are LEDs and then there are LEDs. They can vary widely in their brightness output. For example, these are 2 green LEDs in a 5mm, T-1 3/4, thru hole package. Both are rated at a test current of 20mA.
http://search.digikey.com/scripts/Dk...me=511-1191-ND
This one has a rated output of 100mcd. This is typical of commonly available LEDs, 50 -300mcd.
http://search.digikey.com/scripts/Dk...FPG1-15Q-A3-ND
And this one has a rated output of 34,000mcd.
The output of the 2nd. one is 340 times that of the 1st. And it is not even a matter of price - both of them are about the same. So if the LED is bright enough for you at 20-25mA, just go for it. If not, get a brighter one. No need to mess with paralleling outputs, using BJT's or MOSFETS etc.
Originally Posted by rmteo
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