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Schmidt trigger help

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  1. Nov 12, 2015 #1
    • Poster has been reminded to post schoolwork in the HH forums and use the HH Template in the future
    I have been been trying to search forums and figure out the following question that I just cannot seem to get my head around!

    Design a Schmidt comparator circuit based on an OP07 operational amplifier with the following characteristics: Power supply Voltages: +/- 12V Switching thresholds +1V, -1V

    I have been trying to figure out the voltage saturation and then using this to find the resistor values for the schmidt trigger. I cannot work out what the voltage saturation is and how to calculate it at all.

    Any help would be appreciated, I am really not the best at electronics!

    The following is the circuit I am trying to use modelled on LTSpice:
    upload_2015-11-12_14-37-44.png
     
  2. jcsd
  3. Nov 12, 2015 #2
  4. Nov 12, 2015 #3

    gneill

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    Staff: Mentor

    Consider that you have both +V and -V available since they're powering the op amp. You can tie the bottom of your R1 to -V rather than ground, and add another resistor of the same size as R1 to tie the + input to +V as well. Then tinker with your R2 value to adjust the total spread of the triggers. By symmetry the trigger points should lie on either side of the midpoint between +V and -V, or in other words, 0 V.
     
  5. Nov 12, 2015 #4

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    I would make the power supply rails using two separate sources. Otherwise their relationship to ground can be ambiguous... :smile:
     
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