Compensating tempcos of a photodiode

[Jack Middleton]

Greetings,

I'm running a photodiode with an op amp in a photovoltaic mode. From the
datasheets I can find that the responsivity tempco is 0.35%/C and dark
current tempco is 2X/10C. I wonder how to best compensate for these
effects. Since I have an extra and so far unused ~identical photodiode,
would it be possible to use it (blinfolded) to cancel the temperature
effects of the other one by connecting it to inverting terminal to
cancel the effects of the other one?

Jack Middleton

 

[Jim Thompson]

On Mon, 31 May 2004 22:17:41 +0300, Jack Middleton <nojack@email.com>
wrote:

Greetings,

I'm running a photodiode with an op amp in a photovoltaic mode. From the
datasheets I can find that the responsivity tempco is 0.35%/C and dark
current tempco is 2X/10C. I wonder how to best compensate for these
effects. Since I have an extra and so far unused ~identical photodiode,
would it be possible to use it (blinfolded) to cancel the temperature
effects of the other one by connecting it to inverting terminal to
cancel the effects of the other one?

Jack Middleton

Responsivity is **gain**, so you'd need to compensate for that using
(perhaps) a thermistor. You could probably rig the extra diode to
compensate for the dark current, but I'd have to see your setup before
I could say if the inverting terminal is the place for it.

What I usually do with photo-link situations is use a PWM signal
source and a DC loop to keep the output centered.

...Jim Thompson
--
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