How Multicolor RGB (Red Green Yellow) LEDs Work?
Related Article: Working of Light Emitting Diode (LED)
One commonly used schematic symbol for these LEDs is shown below.
Working of Multicolor RGB LEDs
Multicolor RGB LEDs actually contain two PN junctions that are connected in reverse-parallel i.e. they are in parallel with the anode of one being connected to the cathode of the other.
If a positive potential is applied to the terminal as shown below, the PN junction on the left will light.
Note that the device current passes through the left PN junction.
If the polarity of the voltage source is reversed as shown in the figure below, the PN junction on the right will light.
How Colors are Formed?
Multicolour RGB LEDs are typically red when biased in one direction and green when biased in the other.
If a multicolour RGB LED is switched fast enough between two polarities, the LED will produce a third color.
A red/green LED will produce a yellow light when rapidly switched back and forth between biasing polarities.