Question

Calculate the forward bias current of a Si diode when forward bias voltage of 0.4V is applied, the reverse saturation current is 1.17×10^-9A and the thermal voltage is 25.2mV.

(a) 9.156mA

(b) 8.23mA

(c) 1.256mA

(d) 5.689mA

The question was posed to me in an online quiz.

Asked question is from Characteristic Equation of Diode-1 in portion Diode Circuit of Analog Circuits

Answer 1

Right option is (a) 9.156mA

The explanation is: Equation for diode current

I=I0×(e^(V/ηVT)-1)  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.

I0 = 1.17 x 10^-9A, VT = 0.0252V, η = 1, V = 0.4V

Therefore, I = 1.17×10^-9xe^0.4/0.025 -1 = 9.156mA.