Standard comparators such as LM2903 and LM311 have open collector outputs. I see many times the output of these comparators are tied to Vcc by a pull-up resistor (e.g. in a Schmitt trigger case). Eventhough there is a question about why it is tied to Vcc here: Why do they usually make comparators open collector? I still don't understand the reason.
Anyway my question is not that. It is about calculation of hysteresis. Many times for Schmitt trigger hysteresis calculation I was given the following link: http://www.random-science-tools.com/electronics/inverting-schmitt-trigger-calculator.htm
But this calculator I suppose does not take into account the pull-up resistor.
Would the hysteresis calculation include this pull-up resistor (R3)? Does it have effect on the hysteresis?