# Schmitt Trigger

1. Sep 13, 2006

### Smythersa

HI

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?
v2 and v'2 (please see attachment).

I donâ€™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,
Smythersa

#### Attached Files:

• ###### Schmitt Trigger.doc
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2. Sep 17, 2006

### 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.

3. Apr 11, 2007

### pooface

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?