A thermistor is a type of resistor made from ceramic or polymer materials that exhibits a large, predictable change in resistance when its temperature changes. They come in two main types: NTC (negative temperature coefficient), where resistance drops as it gets hotter, and PTC (positive temperature coefficient), where resistance increases. Engineers use them heavily for temperature sensing, circuit protection, and inrush current limiting.
Heard on the job
Check the NTC thermistor on the power supply; if it blew open, the main cap won't charge.
Insider tip
When replacing a blown NTC thermistor in a power supply, always check the bridge rectifier and switching transistors, as a dead short downstream usually kills the thermistor.
Do not mix it up with
- Thermopile: A thermistor changes resistance with temperature, while a thermopile generates a voltage from a temperature difference.