op-amp integrator, FloydExamp13-10

Discussion in 'Homework Help' started by PG1995, Apr 25, 2012.

  1. PG1995

    Thread Starter Active Member

    Apr 15, 2011
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    Hi [​IMG]

    Please help me with these queries, Q1and Q2, enclosed in the attachments. Thank you.

    Regards
    PG
     
    Last edited: Apr 25, 2012
  2. crutschow

    Expert

    Mar 14, 2008
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    Hysteresis in this case means the output for an input going in one direction is different from the output for the same input going back in the opposite direction.

    For the comparator this means that the trip point for a rising input voltage is higher, do to positive feedback, than the trip point for a falling voltage. This minimizes oscillations due to small noise levels since the noise has to be larger than the hysteresis value (difference between trip points) before the output will change states.

    A similar thing holds true for the BH magnetizing curve of an inductor. The magnetic flux for a rising value of magnetizing current will be different than for the same value of a falling magnetizing current. This is due to the fact that most magnetic materials, even the "soft" ones designed for motors or transformers, retain a small amount of residual magnetism.
     
  3. PG1995

    Thread Starter Active Member

    Apr 15, 2011
    753
    5
    Thank you, Carl.

    So, this means that hysteresis in this context means that the circuit has a kind of memory due to which it knows that its output for an input going in one direction is different from the output for the same input going back in the opposite direction.

    But no definition of 'hysteresis' suggested anything close to "memory", or does it? Though I understand what you have said, I still don't understand why the word 'hysteresis' is used here. Please help me with it. Thank you.

    Regards
    PG
     
  4. crutschow

    Expert

    Mar 14, 2008
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    It has memory to the extend that its input threshold depends upon the state of the output. Whether you think that rigorously fits the technical description of memory or not, hysteresis is the accepted term for that type of circuit operation.
     
    PG1995 likes this.
  5. WBahn

    Moderator

    Mar 31, 2012
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    Look at those definitions again. One of them even specifically states that hysteresis means that the present state is a function of the history and whenever you talk about an effect lagging behind the cause, that means that, somehow, the 'cause' is being remembered.
     
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