The opamp being in positive feedback with Vn @ 4V has an output of 0volts and when the input is a pulse of sufficiently large magnitude that the positive terminal goes high above refernce voltage and output remains at Vcc even after the pulse is removed!
The question is : But,when the pulse is not high enough but still appears positive terminal of opamp , i still see a postive pulse at output in millivolt range, Why does that occur ? Also when i vary the resistor values ,the output pulse magnitude varies and at some point i see positive feedback dominate and take output high forever!! Why?