> Olin, If you need to have a linear output response ( voltage/light ) than
> YOU MUST use a current to voltage operational amplifier converter and
> measure the photodiodes output current rather than output voltage.
> If not, than you'll have a non linear response and a lot of trouble by
> linerising.
> See the Burr Brown optical chips. ( OPT 301 etc...)
> Of course the expensive BB chips could be replaced with cheapers structure
> at the same electrical performance.

Yes, I agree that the voltage of a photodiode is very non linear (closer to
logarithmic) with light intensity.  However, I don't remember the original
poster saying he cared about that.  If you need linearity and high
resolution, then I agree you should amplify the current.  If you don't need
either, you can hook the photodiode directly to the A/D and do the rest in
software.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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