Question

Calculate the reverse saturation current of a diode if the current at 0.2V forward bias is 0.1mA at a temperature of 25°C and the ideality factor is 1.5.

(a) 5.5x 10^-9 A

(b) 5.5x 10^-8 A

(c) 5.5x 10^-7 A

(d) 5.6x 10^-10 A

This question was posed to me during an online exam.

I want to ask this question from Characteristic Equation of Diode-1 topic in portion Diode Circuit of Analog Circuits

Answer 1

Right option is (c) 5.5x 10^-7 A

To explain: Equation for diode current

I=I0×(e^(V/ηVT) – 1)  where I0 = reverse saturation current

             η = ideality factor

             VT = thermal voltage

             V = applied voltage

Here, I = 0.1mA, η = 1.5, V = 0.2V, VT = TK/11600

Therefore, VT at T = 25+273=298 is 298/11600 = 0.0256V.

Therefore, reverse saturation current

IO=0.00055mA = 5.5×10^-7A.