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Photodiode Circuit Help

Discussion in 'General Electronics Discussion' started by mrrrk, Feb 10, 2014.

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  1. mrrrk


    Feb 10, 2014
    I was wondering if anyone could help me with a fairly simple circuit design question. I am designing a simple circuit which consists of a UV photodiode and an ambient light photodiode.

    I have found a device online containing the UV photodiode that I plan to use. Here is the schematic: Senser sch.pdf

    The problem is that I do not understand the use of R2 and R3 in the circuit. Most photodetection circuits that I have seen omit the use of these resistors. I was wondering if anyone could explain why they are included in the circuit? The circuit shown in the schematic is meant to interface with an Arduino. Could it be that R2 (at the output) is to eliminate reflections in the transmitted signal? I am clearly guessing.

    I would get very grateful for any help!
  2. mursal


    Dec 13, 2013
    Unless I'm mistaken R1, R2 and R3 are the feedback network to control the gain of the amplifier.
  3. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Yes correct this will still work without the 1K but the gain is reduced because the 1K lowers the feedback fraction which requires more output voltage to balance the inputs. The 0.1uF prevents oscillations due to input and output capacitance.
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