Op-Amp Supply voltage

Discussion in 'General Electronics Chat' started by dtow1, Apr 30, 2010.

  1. dtow1

    Thread Starter New Member

    Apr 27, 2010
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    0
    Hello,

    I am just wondering if anyone knows of any issues with running an op amp constantly at its supply voltage. Is that in any way damaging to the op-amp? Im thinking about a comparator that is running with a dc input voltage on one of its pins that forces it to run at its positive supply voltage entirely. Is this damaging to the op-amp?

    Thanks,

    Dtow1
     
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    As long as the supply voltage is within the device's ratings and you are not drawing excessive current from the output, it will not be a problem.
     
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  3. kingdano

    Member

    Apr 14, 2010
    377
    19
    i have to disagree - but only because that usually is in violation of the op-amps characteristics.

    generally speaking all op-amps require some headroom on the rail voltages when compared to the input voltage.

    even if you had a +12V supply rail and applied a +12V signal the signal would only reach within a certain amount of the rail (typically on the order of 1-2V)
     
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  4. dtow1

    Thread Starter New Member

    Apr 27, 2010
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    0
    Thank you very much, that is very helpful.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It would be most helpful if you would post your circuit.

    Some opamps have rail-to-rail inputs, and some also have rail-to-rail outputs.

    As kingdano implied, many older opamps and comparators cannot "see" inputs that are within a few volts of the positive supply rail. Some can't see inputs that are within a couple volts of the negative supply rail.

    You can use resistors and/or pots as voltage dividers to keep your input within the range of the opamp or comparator in question.
     
  6. kingdano

    Member

    Apr 14, 2010
    377
    19
    sgt wookie is correct - but without an op amp model or circuit i steered towards general op-amp behavior.


    thanks for clarifying sgt.
     
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