Light emitting diode
From ScienceZero
Driving
The best method to drive a LED is with a fixed current. A LED can also be driven with an exact fixed voltage or an inexact fixed voltage that requires a series resistor to get the correct current. The series resistor can be calculated with this formula:
- <math>R_s = \frac{V - V_f}{I_f}</math>
Where Vf is the forward voltage drop accross the LED and If is the current through the LED. Both values can be found in the datasheet for the LED. For a red LED the typical values are 1.8V and 20mA.
Efficiency
The efficiency of a LED depends on the type but is comparable to a high efficiency incandecent lamp. A coloured LED can be much more efficient than an incandecent lamp because the LED does not need a coloured filter that absorbs all the unwanted colours.
