Diffusion Capacitance is Present in


Diffusion Capacitance is Present in:

  1. Reverse-biased p-n junction diode
  2. Forward-biased p-n junction diode
  3. Unbiased p-n junction diode
  4. Reverse-biased zener diode


The correct option is (2)
Diffusion Capacitance is present in the forward-biased p-n junction diode
because the movement of the charge carriers (electrons and holes) happens in the forward-biased diode, and the diffusion capacitance depends on the storage and movement of excess charge carriers.


The minority carriers (electrons in the p-type region and holes in the n-type region) do not immediately recombine. Instead, they diffuse away from the junction into the respective regions before recombining with the majority carriers. This diffusion process results in the temporary storage of charge carriers within the semiconductor material, which causes diffusion capacitance.

Diffusion capacitance (𝐢𝐷​) is the capacitance due to the storage of excess minority carriers in the forward-biased region of the diode.


The above formula shows that the diffusion capacitance is proportional to the forward current rate of change and the carrier’s lifetime. Therefore, the diffusion capacitance exists when the diode is forward-biased.

Q.1. Diffusion Capacitance of PN Junction diode_________

Q1. In a semiconductor diode, the cut-in voltage is the Voltage_________
Q2. Why does a diode only conduct in one direction?
Q3. The cut-in voltage for silicon diode is approximately

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