Table of Contents
Op amps have an output voltage is determined by the voltage at 2 inputs.
Schmitt triggers make it so that the input voltages move slightly further away from each other at the moment that the output changes.
Op amp comparator Schmitt trigger feed back some of the output voltage to the (non inverting) + input.
A higher + (non inverting) input voltage than the – (inverting) input voltage will result in a high output. Feeding a little bit of that output voltage to the + input makes the + input voltage a little bit higher than it would have been without feed back. So, the + input has to be lowered extra far to fall below the – input voltage, in order to set the output low.
And then, a low output pulls the + input signal voltage a little bit lower, so that is has to be raised an extra amount, to get above the – input voltage, to set the output high.
Hysteresis is the range of extra voltage that the + input signal has to provide in order to overcome the positive feedback from the output.
- Lower value positive feedback resistor will provide less hysteresis.
- Larger value positive feedback resistor will provide more hysteresis.
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