To save potential confusion let me start by saying I just started learning opamp theory about a week ago. I'm currently familiar with inverting, non-inverting, summer, and difference opamps.
My (fairly new) understanding of zero crossing detectors is that when the input signal crosses from positive to negative or vice versa the polarity of output of the opamp will change as well. Essentially it's useful for converting something like a sine wave to a square signal.
If my understanding is correct then what happens if noise is introduced on the input line? I understand better with examples and numbers so let's say I know my noise oscillates over 0v at 100mv peak to peak. How would you account for that?
EDIT: If possible a schematic drawing of a before and after case for handling the noise would be extremely helpful!