Light Emitting Diodes

Light emitting diodes are available in a wide variety of shapes and sizes, and they can be manufactured to fulfil a specific purpose or for general use. In size, they range from a miniature decimal point for use in multi-number configuration to a three-inch high single character display.


The A diagram shows the PN junction encapsulated in clear plastic with the light from the device focused by a lens.  The lens is usually made of self-colored plastic to match, or modify slightly, the colour being emitted by the junction.  The lens can be made to focus the light to a small pinpoint or to spread it over a wide area.

More detailed drawing of the PN wafer of the light emitting diode is shown in B, from this diagram, it can be seen that one face of the silicon is left clear of any obstructions or connecting wire which may impede the path of the light rays.  For a single indicator diode, the junction uses a square section of silicon.  During manufacture it is considerably easier to slice the silicon die into squares than it is to cut and trim complicated shapes; the desired outward appearance of the LED can be more easily obtained by shaping the lens of the device.  Thus, from a square section of silicon, plastic lens caps of square, rectangular, circular or star shape can achieve the shapes required for a particular indicator.