NTC - Thermistor

NTC thermistors (Negative Temperature Coefficient) are a type of resistor whose resistance decreases as the ambient temperature increases. They are often used as temperature sensors. However, the resistance does not change linearly with temperature, but instead follows an exponential curve. Therefore, some calculations may be required to determine the actual temperature from the measured resistance.
The ICL thermistor is an NTC thermistor used as an Inrush Current Cimiter (ICL). Unlike a NTC used for temperature measurement, an NTC ICL is intended to be placed in series with the supply, typically at the mains or DC input of a power supply. At power-up the thermistor is cold and therefore has a relatively high resistance, which limits the initial inrush current that would otherwise occur when, for example, large capacitors are charged. As current flows through the thermistor it heats up due to its own power dissipation, the resistance drops significantly, and the voltage drop across the component becomes small during normal operation.