Explain the different equivalent circuits for semiconductor diode
Answers
Answer:
1)AC Equivalent Circuit of Semiconductor Diode:
Junction Capacitance:The depletion region of a pn-junction is a layer depleted of charge carriers situated between two blocks of low resistance material. Because this is the description of a capacitor, the depletion region clearly has a capacitance. The depletion layer capacitance (Cpn) may be calculated from the equation for a parallel-plate capacitor if the junction dimensions are known. Typically, Cpn is 4 pF for a low-current diode.
2)AC Equivalent Circuits (Reverse- and Forward-Biased):
A reverse-biased diode can be simply represented by the (high non-constant) reverse resistance RR in parallel with the depletion layer capacitance Cpn, The AC Equivalent Circuit of Semiconductor Diode for a forward-biased diode consists of the dynamic resistance rd in series with a voltage cell representing VF. To allow for the effect of the diffusion capacitance, Cd is included in parallel. This gives the complete equivalent circuit shown below:
