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| Photodiode circuit design |
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| StillTrying:
I've found the light shape from reds to be slower and curved, and super bright green and blue the fastest and squarest. I won't be trying to get the fastest speeds out of the green and blues because I've got a 100W white COB waiting for >>100W testing! |
| jlmoon:
Just a curious question, how come you're setting the gain on 2nd op amp to 6.8? Wouldn't it be ok to set that to unity or 1? Using the 2nd amp as a follower or buffer only? |
| stcoso:
--- Quote from: StillTrying on March 30, 2019, 07:40:00 pm ---I've found the light shape from reds to be slower and curved, and super bright green and blue the fastest and squarest. I won't be trying to get the fastest speeds out of the green and blues because I've got a 100W white COB waiting for >>100W testing! --- End quote --- I've tried also with some green led and found them slower. I used an IR led and it was the fastest. I'm trying to build this little probe because i need it to measure a UV source (20W 365nm) that i've already built and rise/fall time are really important. I suppose :D white LED are really bad (microseconds?) at turning on/off because of phosphorescence (turn off especially). |
| stcoso:
--- Quote from: jlmoon on March 30, 2019, 07:55:52 pm ---Just a curious question, how come you're setting the gain on 2nd op amp to 6.8? Wouldn't it be ok to set that to unity or 1? Using the 2nd amp as a follower or buffer only? --- End quote --- Short and thruthful answer: basically i don't know what i'm doing :-DD ... but, as i (maybe wrongfully :D) understood to achieve higher bandwidth without compromising stability and noise i needed lower gain in the first stage. |
| StillTrying:
"white LED are really bad (microseconds?) at turning on/off because of phosphorescence (turn off especially)." As long as they're not warm white, white LEDs are faster than that ~160ns. The last 2 pics in my link above reply#8 are RedGreenWhite5mm.gif and UV+Blue LED.gif The UV edges are fast. "Short and thruthful answer: basically i don't know what i'm doing" Join the club! |
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