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Photodiode amplifier

Discussion in 'Electronic Design' started by John Popelish, Jul 15, 2003.

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  1. I have gotten very helpful responses to my last thread on speeding up
    a photo diode amplifier for infrared radiation, specifically,
    improving the recovery time to full dark sensitivity, following a
    flash.

    I have incorporated several suggestions with a few changes and posted
    to alt.binaries.schematics.electronic under the the same thread
    title. I built this, today, but will first apply power tomorrow. Any
    predictions on the result? "[email protected]

    The switch indicates that the bias filter capacitor multiplier can
    either filter the bias voltage with respect to ground, or with respect
    to the current to voltage amplifier inverting input in a bootstrap
    configuration.

    I haven't tried any variation of the bootstrap, yet, so I may get some
    surprises.

    In summary:
    I am now expecting to have to apply considerable bias voltage, either
    because I will be using an avalanche diode, or to deplete the junction
    in a PIN diode. I have learned that silicon is fairly transparent to
    infrared near the long wave limit of sensitivity, so lots of charge
    carriers are produced deep in the doped base of the diode. These
    carriers slowly diffuse into the depleted or intrinsic layer, before
    they show up as photo current, adding a slow tail to the diodes
    response, and this has been giving me indigestion.

    Thanks again to all who have contributed, so far.

    Any comments on this version or suggestions for alternatives are
    welcomed.
     
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