# How Multicolor RGB (Red Green Yellow) LEDs Work?

- Link: https://studyelectrical.com/2017/11/how-multicolor-red-green-yellow-leds.html
- Published: 2017-11-20T07:01:00+00:00
- Author: 

![](https://2.bp.blogspot.com/-rOwOHQUQZKw/WhJ1bIQqd9I/AAAAAAAACWk/yJibqF43W3cShMZOKWEARtZ4VoGSbwfHgCLcBGAs/
s1600/51V%252BxM1CQ2L.01_SL500_.jpg)

A Light Emitting Diode that emits one color when forward biased and another color
when reverse biased is called a multicolor RGB LED.

> Related Article: [Working of Light Emitting Diode (LED)](http://www.studyelectrical.com/2017/11/working-of-light-emitting-diode-led.html)

One commonly used schematic symbol for these LEDs is shown below.

 

![Multicolor RGB LED Schematic Symbol](https://2.bp.blogspot.com/-JReeHkKprvA/WhJ2aK5b0PI/
AAAAAAAACWs/rdUtTyYQb_oXgFqBVrozlDXJzOc3rrjGgCLcBGAs/s1600/multi%2Bled%2Breverse%
2Bbiased.PNG "Multicolor RGB LED Schematic Symbol")

Multicolor RGB LED Schematic Symbol

 

## 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.

 

![Working of RGB LED](https://2.bp.blogspot.com/-lWDaHY9VoNA/WhJfd-iv7AI/AAAAAAAACWQ/
Q_PSfu78cUsvvOpwLvQoljRyvg170M58gCLcBGAs/s1600/multicolor%2Bled.PNG "Working of 
RGB LED")

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.

![multi%2Bled%2Breverse%2Bbiased](https://3.bp.blogspot.com/-_RzvBbIB-CY/WhJfk15SnbI/
AAAAAAAACWU/qqzVqwTDsiseRq_L3AsVnyNrV5GS2j3UQCLcBGAs/s1600/multi%2Bled%2Breverse%
2Bbiased.PNG)

Note that the direction of device current has reversed and is now passing through
the right PN junction.

### 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.

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