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OP Amps Comparators

  1. Oct 24, 2015 #1
    1. The problem statement, all variables and given/known data
    https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/73/73750-4bf3d2aa03a724fcf0b13a6b1111902f.jpg [Broken]


    3. The attempt at a solution
    V+ > V- for Vout to be +16V
    V+ < V- for Vout to be -16V
    V+ = -8x(in)
    V- = (-15x18)/30 + (15x12)/30 = -3
    My attempt on it was that -8X(in)V greater or equal to -3V for Yout to +16V
    (EDIT: Then that would be Xin < 0.375 for it to be +16V
    But the answer is saying the opposite.)

    But this was the solution and it showed the opposite (that -8x(in) less that or equal to -3)

    https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/73/73751-f11fe983c5d64cca6eb97cffb930e594.jpg [Broken]This was the answer
     

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    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Oct 24, 2015 #2

    CWatters

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    Do you mean.. Yout is 16V if -8X(in)V greater or equal to -3V ?

    In which case that is correct.

    Their solution looks correct to me. As a check try setting Xin = 1V and work out Xout, Yin, Y+ and Yout.
     
  4. Oct 24, 2015 #3
    My mistake for not completing my answer.
    And yes, that's what i meant, When -8(xin) was greater than -3 then the Vout would be +16V
    Then that would be Xin < 0.375 for it to be +16V
    But the answer is saying the opposite.
     
  5. Oct 24, 2015 #4
    Yout is -16V when Xin < 0.375
     
  6. Oct 24, 2015 #5

    CWatters

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    No the graph shows that when Xin is < 0.375 then Yout is +16v. For example at t=0.
     
  7. Oct 24, 2015 #6

    rude man

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    The output graph is wrong. The transition of Yout going from -16V to +16V occurs when Xout = -3V, not -1V as shown.
     
  8. Oct 24, 2015 #7

    rude man

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    No.
     
  9. Oct 24, 2015 #8
    Sorry guys, I just read the graph incorrectly.
    Thanks for pointing that out.
     
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