Light Emitting Diodes

• LED's are diodes that will produce light when biased correctly. The graphic symbol for an  LED is given in figure.

• LED's are available in various emitting colors as well as infrared( which is not visible), green, red, orange, yellow, and blue, the schematic symbol is the equal for all colors. As LED's have obvious cases, there is usually no label on the case to find the leads.
• The leads are generally in one of three forms

(1)   The leads may have dissimilar lengths.

(2)   One of the leads can be flattened. The flattened lead is generally the cathode.

(3)   One portion of the case might be flattened, the lead nearest to the flattened side is generally the cathode.