A low-frequency oscillator using PTC and NTC thermistors

A mathematical model and analysis method for discrete parameter thermistor networks are developed. Methods for predicting the static conditions and the stability and sensitivity of the equilibrium points are given. The dynamic behavior is discussed using numerical analysis methods. Experimental results have been obtained to verify the analysis methods for the case of oscillatory behavior. The analysis method is then used to predict the behavior of the oscillator as the applied voltage, thermal capacitance, dissipation factor, and ambient temperature are varied. It is concluded that the mathematical model and analysis methods predict the behavior of the discrete parameter thermistor networks. The temperature gradients in the elements in still air appear to be negligible, but caution must be used in applying the methods to those networks where the temperature gradients may not be negligible.