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op amp and photo diode

Discussion in 'General Electronics Discussion' started by jerk, May 23, 2013.

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  1. jerk

    jerk

    16
    0
    Oct 13, 2010
    I need to detect room luminosity. I was thinking to use normal LED and op amp to bring the signal to PIC adc.
    Will the selected op amp in the below circuit be OK?
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,424
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    Nov 17, 2011
    No, the 741 will not operate from a single supply with an input signal near ground.
    Use a dual supply (e.g. +-5V). You can easily generate -5V from +5V using a switched capacitor voltage inverter.
    You may also wan t to use a modern OpAmp with better technical data, as the venerable 741 is rather outdated.
     
  3. jerk

    jerk

    16
    0
    Oct 13, 2010
    can you suggest some modern op amp where I can use same power supply as for the PIC - 5VDC.
    But it has to be large enough I can hand solder it to my PCB (5SOT23 are not an option). I was looking Farnell store and all I could find to be suitable for hand soldering were DIP types, for example MCP6271-E/P.
     
    Last edited: May 23, 2013
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,424
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    Nov 17, 2011
    You can try almost any operational amplifier with rail to rail input and low bias current, e.g. the OP184 or a similar type (Google: rail-to-rail input operational amplifier)
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Microchip make a whole range of op-amps that are designed to run from 5V and have rail-to-rail outputs, and often, inputs as well. Look on microchip.com under op-amps.
     
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