positive temperature coefficient (electronic) (PTC)
PTC thermistors are heat-sensitive, nonlinear resistors with a positive temperature coefficient. In contrast to thermistors, the resistance of PTC thermistors increases as the temperature rises.
PTC thermistors, Positive Temperature Coefficient (PTC), conduct current better at low temperatures. PTC thermistors are available in resistance values from 1 ohm to 100 kilo-ohms. Temperature ranges are from -65 °C to +200 °C and the temperature coefficient is as low as 1%/°C.
They are made of electroceramic materials such as barium titanate( BaTiO3) and are used for temperature compensation in power supplies, devices and of electronic components and prevent overheating in high-power LEDs.
For PTC thermistors there is still the term posistor. This is a protected designation of the company Murata.