A Thermistor IC (thermal resistor) is a semiconductor device that is used in a wide range of circuits, including surge protection. Often used for temperature measurement as well as current-limiting control.  Thermistors change their resistance based on the temperature. There are two types NTC and PTC and the resistance will change depending on the temperature. They are used in a variety of applications, such as temperature control, heating control and sensing. RS can offer products from leading manufacturers including EPCOS, Vishay, TE Connectivity, Panasonic, KYOCERA AVX, Molex, Murata and many more.

There are two semiconductor types, these are both based on the temperature coefficient.

• Negative Temperature Coefficient (NTC) Thermistor: An NTC thermistor’s resistance decreases as the temperature rises and can be found in applications such as low-temperature measurements of temperature sensors, as well as inrush current limiters.
• Positive Temperature Coefficient (PTC) Thermistor: A PTC's thermistor resistance increases as the temperature rises and can be found in applications such as overcurrent protection

A Thermistor is a temperature-sensing device. Available in different formats including disc, bead, and chip either through hole or surface mounted (SMD) usually encapsulated in epoxy resin, paint, glassed or phenolic and can be mounted or fixed into the system needing monitoring. See Sensors-Thermistors