POF photodiode help

Thread Starter

tronicsguy

Joined Oct 6, 2005
9
I am designing a voltage to light and light to voltage transducer.
They have to be linear.
For the V to Light, I used an op amp. Similarly for the L to V, I used an op amp.

At the light to voltage end, I am using the IFD 91 photodiode. I am not getting a linear response at this end. something like an S curve. Its not linear at the lower end and the higher end.
I don't have a light meter. So I am measuring the voltage at the output of the op amp.
Are photodiodes not linear?
Any ideas/suggestions to correct this.

TIA.
 

beenthere

Joined Apr 20, 2004
15,819
Hi,

First of all, get the mfr's specs on the photodiode. That will tell you about the non-linearity issue. That document will also suggest a typical circuit for a maximally linear output.
 

Thread Starter

tronicsguy

Joined Oct 6, 2005
9
Originally posted by beenthere@Oct 7 2005, 08:33 AM
Hi,

First of all, get the mfr's specs on the photodiode. That will tell you about the non-linearity issue. That document will also suggest a typical circuit for a maximally linear output.
[post=10854]Quoted post[/post]​
I already did contact the manufacturers. No reply yet.
The data sheet does not have a typical ckt.
 

Thread Starter

tronicsguy

Joined Oct 6, 2005
9
Originally posted by tronicsguy@Oct 7 2005, 08:36 AM
I already did contact the manufacturers. No reply yet.
The data sheet does not have a typical ckt.
[post=10855]Quoted post[/post]​
I got the datasheet, but it was of no use. No typical ckt ideas.
The response of the photodiode is initially (first 40% of the full scale). I just decided to use the output after it crosses this scale.
 

beenthere

Joined Apr 20, 2004
15,819
Hi,

I seem to remember that photodiode circuits had lots of resistance. I think the PD is happy running in low microamp regions. A stable FET input op amp will be the thing to use.
 
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