Question

A diode had a transition capacitance of 1pF and depletion width of 1 µm. The capacitance changes to 10 pF when the depletion width changes. The final depletion width is __________

(a) 10 µm

(b) 0.1 µm

(c) 1 µm

(d) 100 µm

This question was addressed to me in an interview.

This intriguing question originated from Transition Capacitance in portion Diode Circuit of Analog Circuits

Answer 1

The correct option is (b) 0.1 µm

Best explanation: The equation of transition capacitance = ƸA/W

Where Ƹ = permittivity of the material of diode, W = depletion width

            A = area of cross section

Since depletion width and capacitance are inversely proportional

Depletion width decreases to 0.1 µm.