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Op amp question

  1. Mar 13, 2014 #1
    1. The problem statement, all variables and given/known data

    What is the output voltage for an op amp whose non-inverting input is connected to ground and its inverting-input voltage is 4mv? Assume that the op-amp open-loop gain is 2*10^5 and its supply voltage is Vcc=10V

    2. Relevant equations
    Vo= A(vp-vn)


    3. The attempt at a solution
    The problem gives
    Vn= 4mv
    A=2*10^5
    Vcc=10V
    Since it says the non-inverting input is connected to ground, does that mean vp=0?
    Vo=2*10^5(0-.004V)
    Vo=-800 V
    However the answer is suppose to be -10V. What am I doing wrong?
    Thanks for helping!
     
  2. jcsd
  3. Mar 13, 2014 #2

    gneill

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    Staff: Mentor

    Can the output of an op-amp ever exceed its power supply voltages (positive and negative supplies)?
     
  4. Mar 13, 2014 #3
    Ahh, I see so the max Vo is 10 and min Vo is -10. So is what I did wrong? Do I have the write down that calulated vo= -800 but say the min is -10V.
     
  5. Mar 13, 2014 #4

    gneill

    User Avatar

    Staff: Mentor

    That's the idea. Do the calculation and then state why in actuality the value will be "truncated" by the limits imposed by the power source.
     
  6. Mar 13, 2014 #5
    Thank you so much!
     
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