Question

On which of these does the diffusion capacitance of a diode not depend upon?

(a) Forward current

(b) Dynamic conductance

(c) Doping concentration

(d) Reverse resistance

This question was posed to me in examination.

This question is from Diffusion Capacitance topic in section Diode Circuit of Analog Circuits

Answer 1

Right option is (d) Reverse resistance

The explanation: CD = \(\frac{εA}{W}\) which means CD ∝ \(\frac{1}{W}\). Thus, CD ∝ \(\frac{1}{\sqrt{Doping}}\) concentration

CD = τg = \(\frac{τ}{r} = \frac{τI_F}{ηV_T}\)

where τ = carrier life time, g = dynamic conductance, IF = forward current.