Help with LEDs! - maximum rise and fall times

[Tomby]

Help with LEDs!!!!

Hi friends,

I need to find out how or where I can get the maximum rise and fall times for some specific LEDs. I got the datasheet from the manufacturer but they don't seem to have this info on the datasheet. I just want to know exactly how fast I can modulate the signal on the Leds(i.e. like IR communications). Thanks.

 

[Fragrance]

Re: Help with LEDs!!!!

hi


Please check out this link for information

https://www.commlinx.com.au/IR.htm

 

[House_Cat]

Re: Help with LEDs!!!!

The parameter you are looking for is cutoff frequecy. It gives you the 3db point for response to sine wave modulation.

LED's intended for communication include the value in the spec sheet. For common illumination LED's the manufacturers don't normally list cutoff frequency because the user doesn't care. Typically they have values somewhere in the range of .1-10MHz. For example: h**p://usa.hamamatsu.com/hcpdf/catsandguides/Led.pdf

Communication LED's can have cutoff frequencies of 50MHz or more. For example: h**p://www.rohm.com/products/databook/s/pdf/sir-568st3f.pdf

The short answer is that you pick the diode that will do the job. If you want to use common inexpensive LED's you already have, you will have to experiment to see what you can squeeze out of them. You can overdrive in pulsed operation to get shorter response times, but you have to be careful not to overheat the junction.