Question

The resistance (R) of an NTC thermistor varies with temperature according to R =R∞exp(B/T). Calculate the critical maintained voltage drop across the thermistor above which thermal runaway would occur for an ambient temperature of (i) 300K and (ii) 360 K. The thermistor characteristics are as follows:

R = 4.5 x 10-3 W, B= 3000 K; 1/kth = 3.3 x 10-2 WK-1.