Question

If the current I is 2mA then find the temperature at which diode operates. The cut-in voltage of diode is 0.6V. The reverse saturation current of diode is 10^-9A. Resistance R is 1.3KΩ.

(a) 45.85°C

(b) 50.47°C

(c) 60.26°C

(d) 56.89°C

The question was posed to me in class test.

This interesting question is from Characteristic Equation of Diode-2 topic in portion Diode Circuit of Analog Circuits

Answer 1

Right answer is (a) 45.85°C

The explanation is: Equation for diode current

 where I0 = reverse saturation current

             η = ideality factor

             VT = thermal voltage

             V = applied voltage

Since in this question ideality factor is not mentioned it can be taken as one.

VD = 3-(2mAx1.3k) = 0.4V

VT = T/11600

Thus Temperature, T = 11600×0.0275 = 319 Kelvin = 45.85°C.