Thermistor

A thermistor is a type of resistor whose resistance changes rapidly with temperature. The word 'thermistor' is derived from "thermal" and "resistor". They are temperature sensors.

Picture of a thermistor

Thermistor symbol

Types of Thermistors

There are two kinds of of thermistors:

• NTC (negative temperature coefficient) 
• PTC (positive temperature coefficient)

The major difference between the two types of thermistors is their reaction to temperature changes. The resistance of NTC (negative temperature coefficient) decreases with an increase in the surrounding temperature while the resistance of PTC (positive temperature coefficient) increases with an increase in the surrounding temperature.

There is a sudden change in the resistance of NTC thermistors whenever a slight change in surrounding temperature occurs; this makes NTC thermistors ideal for temperature measurement.

Thermistor Applications

Temperature control circuits

Temperature measurement circuits

Circuit Protection