FreeLists / si-list / [SI-LIST] LED measurements

["KS Lau" <k.s.lau@xxxxxxxxxxxxxxx>]

Dear si-ers,

I'm wondering if this question is proper for this forum.


I'm curious to know how the industry measure the bandwidths of high-speed LEDs. 
I've spoken to a particular manufacturer and apparently they do start measuring 
the LED's bandwidth from 100kHz onwards.

I measured a normal red LED using my transimpedance front-end which has a 
bandwidth of 300Hz - 20MHz and found that my red LED has approximately 3MHz 
bandwidth. But the response isn't flat in the low-frequency region and there's 
a slight hump in the 300Hz - 10kHz region.

   /---\
  /     \------\
 /              \
/                \
300Hz  10kHz   3MHz

The response looks something like this.

I hope this post is suitable.

Regards,
Keng San


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