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PIN photometer 3

Discussion in 'Electronic Basics' started by Dominic-Luc Webb, Feb 28, 2004.

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  1. John Larkin

    John Larkin Guest

  2. Jamie

    Jamie Guest

    after checking INtels specs on that OPAMp i don't think it
    can work because it does not appear to have any internal self
    biasing, if the diode was generating energy then i would say
    yes it would create a rail-rail output but still not useable.
    its my opinion that you need feedback resisters.

    Btw.
    nice pre'amp to use on Hi-z projects..
     
  3. Thanks for all responses. I know with a single 0.82 pF cap
    as feedback using a single opamp, these work, but I was
    hoping to get more gain. Maybe you know some very simple
    example circuits to amplify using a second opamp that
    would not risk losing linearity?

    Also, it seems that input bias current increases with
    temperature (from specsheet of LMC662). I wonder if
    anyone ever puts these inside a cooling unit to keep
    the temp down, and thus, the input bias?

    Dominic
     
  4. Dominic-Luc Webb wrote...
    Dominic, the circuit fails to function because it is
    *nonsense* and not because of the properties or size
    of any of its components. Please study the subject
    a bit more, and read up on resistors. Very handy.

    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
  5. Might I recommend "Photodiode Amplifiers: OP AMP Solutions" by Jerald
    Graeme. ISBN 007024247X. See info on T-networks for high gain
    feedback with smaller resistor values.

    Also "Building Electro-Optical Systems: Making It All Work" by Philip
    Hobbs (ISBN 0471246816) is a great resource.

    Steve J. Noll | Ventura California |
    | The Used High-Tech Equipment Dealer Directory
    | http://www.big-list.com
    | The Peltier Device Information Site:
    | http://www.peltier-info.com
     


  6. Thanks for these leads! I just now searched and found both books
    from local technical library and also from local mail order business.
    In case these books do not cover this (most do not), do you know if
    dark current can be reduced significantly in a PIN? Can they survive
    and operate with nitrogen cooling? I am thinking to place the PIN
    inside an aluminum housing and to have cooling lines for nitrogen
    running through the aluminum block. Any ideas?

    Again, application is measurement of red/infrared from faint stars from a
    telescope.

    Dominic
     
  7. Choose the smallest active area that will still capture all of your
    signal. Sort several detectors for lowest dark current.
    But, I think if noise is your concern that other noise sources, like
    the transimpedance amp feedback network, might be a bigger concern.
    Others on this forum may be more qualified to comment on this.
    I'm almost certain that they will operate fine that cold. Mechanical
    damage from too fast thermal shock is probably the only concern.
    But this adds the significant problem of forming frost on the detector
    housing window, so a lot of dry nitrogen gas flushing would be needed.

    I have seen output offsets from high gain transimpedance amps
    (>=1G) significantly reduced by flushing the amp housing with dry
    nitrogen. Reduced the leakage paths - which were most significant
    across the op amp package surface - more than across the feedback
    components. It can make a dramatic difference. Painting everything
    with red corona dope helps too once the surfaces have been cleaned
    and the leakage tested.

    Steve J. Noll | Ventura California |
    | The Used High-Tech Equipment Dealer Directory
    | http://www.big-list.com
    | The Peltier Device Information Site:
    | http://www.peltier-info.com
     
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