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Homework Help: Schmitt Trigger

  1. Sep 13, 2006 #1

    I don't think my question is very difficult. I understand what a Schmitt Trigger is and what it does. There is, however, a couple of calculations that I've long forgotten and need to know. I am currently doing an own time study course at work.

    How do I calculate the following?
    the dead zone (hysteresis),
    v2 and v'2 (please see attachment).

    I don’t know if I should supply you with either or both Vout or a Vref . Please use values if it is required. I only need an example in order to understand the calculations.

    Thanks a million. I've done this years ago.

    Kind regards,

    Attached Files:

  2. jcsd
  3. Sep 17, 2006 #2


    User Avatar

    Staff: Mentor

    Just calculate the + input voltage to the comparator when its Vout is at each of the rails (a rail-to-rail comparator seems to be assumed in the figure). Assuming that the comparator has no built-in hysteresis of its own (most don't, some do), then the two switching points are just at those two voltages, and the dead zone is between them.

    Just think of a Schmidt trigger as a comparator with positive feedback through a voltage divider, as shown in your figure. The positive feedback is what makes it so the signal has to go back some amount after causing a switch, to get through the hysteresis region.
  4. Apr 11, 2007 #3
    I also need help with this.

    can someone do some examples with the given circuit?
    let the values given be as they are.

    umm and the input be a sine 8vp-p.

    when i am analyzing the circuit and say vin is +4vp. Do i do a voltage divider with -6VSAT or 6VSAT?
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