Overview of Thermistor Working Principles

Key Mechanisms:

1. ​​Negative Temperature Coefficient (NTC)​​

   • ​​Resistance decreases exponentially as temperature rises​​:
     • Caused by increased ​​carrier concentration​​ (electrons/holes) in semiconductors at higher temperatures 
        
     • Example: NTC thermistors are used for temperature measurement and overcurrent protection 
   • ​​Formula​​:
     RT​=R0​⋅eB(T1​−T0​1​)
     Where $B$ is a material-specific constant, and $T$ is the absolute temperature 
      

2. ​​Positive Temperature Coefficient (PTC)​​

   • ​​Resistance increases sharply at a critical temperature​​ (e.g., BaTiO₃-based ceramics):
     • Due to ​​phase transitions​​ or ​​barrier height changes​​ at grain boundaries 
        
     • Applications include overcurrent protection and self-resetting fuses 
        

Material and Design:

• ​​Semiconductor ceramics​​ (e.g., BaTiO₃, MnO₂) are sintered to create a porous structure with high resistivity and sensitivity 
   
• ​​Doping​​ with rare earth elements (e.g., Y, La) enhances performance by adjusting resistivity and temperature coefficients 

Applications:

• ​​Temperature sensing​​: High accuracy in narrow ranges (-50°C to 300°C) 
   
• ​​Circuit protection​​: PTC thermistors limit current during overloads 
   
• ​​Self-heating systems​​: NTC thermistors stabilize temperature in devices like air conditioners 
   

For detailed technical specifications (e.g., B-values, time constants), refer to manufacturer datasheets or standards like IEC 60539 .