Explanation : The forward characteristic of an LED is similar to an ordinary junction diode. The diode starts conducting only after the forward-bias voltage overcomes the barrier potential. Thereafter the current increases exponentially beyond the knee region.
Led forward characteristic for different LED types and colour
The threshold voltage is about 1.2 V for a standard red LED to about 3.6 V for a blue LED. However, these values depend on the manufacturer because of the different dopant concentrations used for the different wavelength ranges.
The intensity of the emitted light is directly propotional to the forward current. An LED is operated with a typical forward current of 20 mA- about 5 mA for a simple LED indicator to about 30 mA where a high intensity of light is needed. The LED forward current must be limited to a specified safe value using a series resistance.
The peak inverse voltage (PIV) or breakdown voltage of an LED is low, typically 5 V.
