[SOLVED] How to find ON current for a LED ???

[0by1]

Hi all,

For a LED having Vf=2V, If=20mA,

>Whats the ON current for this LED??
>Is that necessary to limit current to 20mA?? so much current !!!!

Thanks in advance.

 

[umesh49]

Its depend on LED specification/charactersics. 20mA should be average DC current allowed and there should be a peak current rating also. If you are controlling the LED with a transistor and PWM at base then Imax*duty should be less than 20mA at 25`C. This average current capabillity will reduce at higher temperature depend on derating curve of LED.

Umesh.

 

[alexan_e]

You can drive the led with a lower current if you want which will result in lower light intensity, there is no problem at all as long as you are satisfied with the result.

Alex

 

[0by1]

Thanks Alex and Umesh, got the answer.

consideration factors for ON current of a LED
> it should be bright enough
>life of a LED
>should be less than max. forward current.