Heater for aerosol-forming substrate comprising a positive temperature coefficient thermistor

A heater for heating an aerosol-forming substrate, the heater comprising:

• a heating element configured to heat the aerosol-forming substrate, the heating element comprising at least one positive temperature coefficient (PTC) thermistor, the at least one PTC thermistor being configured to be supplied with an electric current so as to heat the at least one PTC thermistor,
• wherein a resistance of the at least one PTC thermistor increases when a temperature of the at least one PTC thermistor increases within a stabilised temperature range, a lower end of the stabilised temperature range being, when a constant voltage is applied to the at least one PTC thermistor, a reference temperature at which the resistance of the at least one PTC thermistor is twice a value of a minimum resistance of the at least one PTC thermistor, and
• wherein the reference temperature is between about 100 degrees Celsius and about 350 degrees Celsius when a constant voltage of 3.3 Volts is applied to the at least one PTC thermistor.