op amp problem - backwards battery?

Discussion in 'Homework Help' started by spicy_tofu, Oct 17, 2012.

  1. spicy_tofu

    Thread Starter New Member

    Oct 17, 2012
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    having a problem with the 'backwards' battery in this hw problem (circuit is attached). Im thinking there will be no current or Vout since the negative terminal is facing out. It is a 741 opamp
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    The opamp does not have a power supply so it will do nothing.
    If it has a plus and minus 10V or more power supply with the 0V of it connected to the circuit's ground then its output will be +7.2V.
     
  3. spicy_tofu

    Thread Starter New Member

    Oct 17, 2012
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    I think for this circuit it would be zero like you said. It doesn't say anything about ground on the assignment, so im assuming its just earth ground. thanks for your help!
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    One can assume that the 741 is powered with -15V and +15V.

    The battery is not backwards. It presents -8V input.
    Calculate the voltage gain of the inverting amplifier circuit and you should be able to determine the output voltage.
     
  5. catfibres

    New Member

    Oct 17, 2012
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    Indeed, unless it is a "trick question" problem (no power supply for op amp), then a +/-15 volt supply may be assumed. In that case, it is a simple inverting amplifier with an input of -8V and a gain of -0.9, thus the output of +7.2V.
     
  6. bertus

    Administrator

    Apr 5, 2008
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