The output goes high when a preset temperature is exceeded. A fixed half-supply reference voltage feeds a reference current to the inverting input, and a variable current is fed to the noninverting input. Resistor R6 is a negative-temperature-coefficient (NTC) thermistor, so the potential at the junction of R5 and R6 rises with temperature.

The Circuit Diagram of Over-Temperature Switch

 The op amp will switch high when that voltage exceeds the half-supply value. The trip temperature can be preset via R5.