What is a Thermistor?
11 Jul, 2025
A thermistor is a temperature-sensitive resistor whose resistance changes significantly with temperature.
Types of Thermistors:
- By Structure/Shape: Spherical, rod-shaped, tubular, disc-shaped, ring-shaped, etc.
- By Heating Mode: Direct-heating (self-heating) and side-heating (external heating).
- By Working Temperature Range: Normal temperature, high temperature, ultra-low temperature.
- By Temperature Coefficient:
- Positive Temperature Coefficient (PTC): Resistance increases with temperature (e.g., BaTiO₃-based).
- Negative Temperature Coefficient (NTC): Resistance decreases with temperature (most widely used, e.g., MnO₂-based).
- Positive Temperature Coefficient (PTC): Resistance increases with temperature (e.g., BaTiO₃-based).
Key Characteristics:
- High Sensitivity: Resistance changes rapidly with small temperature variations.
- Nonlinearity: NTC/PTC resistance-temperature relationships are nonlinear (e.g., exponential for NTC).
- Applications: Temperature measurement (e.g., thermostats), overcurrent protection (PTC fuses), temperature compensation (in circuits).
Nominal Value Note:
The nominal resistance is measured at 25°C. Actual resistance may deviate due to self-heating or material characteristics. For example, PTC thermistors show a sharp resistance increase above a critical temperature, while NTC thermistors exhibit exponential decay.