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Summing op amp circuit help?

  1. Feb 20, 2017 #1
    1. The problem statement, all variables and given/known data
    Solving for this circuit here, where V = -5V
    upload_2017-2-20_1-16-36.png
    2. Relevant equations
    upload_2017-2-20_1-16-50.png

    3. The attempt at a solution
    I found the equation for a summing op amp like this one, plugged everything in and ended up with -3V, which is marked wrong. I'm really at my wit's end here and the homework has been incorrect in the past so I'm not even sure this is the wrong answer, any help would be appreciated.
     

    Attached Files:

  2. jcsd
  3. Feb 20, 2017 #2
    I think you must have a math error somewhere. Are all the signs correct?
     
  4. Feb 20, 2017 #3
    I think so, I ended up writing it out and still got 3V
     
  5. Feb 20, 2017 #4
    Can you post it?
     
  6. Feb 20, 2017 #5
    Sure 20170220_013527.jpg
     
  7. Feb 20, 2017 #6
    Check the polarity on the 4.5.
     
  8. Feb 20, 2017 #7
    Oh the sneaky bastards...
    I got 6 volts for it thank you for your help!
     
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