What does the Comparator with Hysteresis circuit do?

A feature of this circuit is that its output is not affected even if the input signal contains a certain amount of noise (the output is influenced not only by the present input condition but also by the past input condition, that is, hysteresis).
[Operation]
Hysteresis can be given to the threshold voltage by positively feeding back part of the voltage of OUTPUT to the positive (+) input pin with R₂ and R₁, and the influence of a noise voltage within the hysteresis width can be eliminated.
Specifically, when the INPUT voltage rises with a sufficiently low voltage (), OUTPUT goes high. Consequently, a positive voltage drop occurs across R₁ (i.e., the potential on the pin of R₁ connected the positive (+) input pin is higher than the potential on the pin connected to the VREF pin) and the potential on the positive (+) input pin goes VTH (High). This status is maintained until INPUT reaches this potential VTH (High). As soon as INPUT exceeds VTH (High) (), OUTPUT falls low. At the same time, the voltage drop across R₁ becomes negative (i.e., the potential on the pin of R₁ connected to the positive (+) pin is lower than the potential on the pin connected to the VREF pin), and the potential on the pos itive (+) input pin goes VTH (low). Even if INPUT is raised after that, OUTPUT remains low (). When INPUT is gradually lowered next, OUTPUT remains low until INPUT = VTH (low) (). When INPUT drops below VTH (low) (), however, OUTPUT goes high again, returning to the initial status.