POF photodiode help

Discussion in 'General Electronics Chat' started by tronicsguy, Oct 6, 2005.

  1. tronicsguy

    Thread Starter New Member

    Oct 6, 2005
    9
    0
    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.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    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.
     
  3. tronicsguy

    Thread Starter New Member

    Oct 6, 2005
    9
    0
    I already did contact the manufacturers. No reply yet.
    The data sheet does not have a typical ckt.
     
  4. tronicsguy

    Thread Starter New Member

    Oct 6, 2005
    9
    0
    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.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    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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