Current control devices, load characteristics similar to the PN junction of the UI curve, the very small change of the positive guide pass voltage will cause a large change in the forward current (exponential level), the reverse leakage current is very small, there is a reverse breakdown voltage. In actual use, you should select. The forward voltage of LED decreases with the increase of temperature and has a negative temperature coefficient. LEDS consume power and part of it translates into light energy, which is what we need. The rest is converted into heat energy, which raises the junction temperature. The heat emitted (power) can be expressed as.