What is the formula for dynamic resistance of a diode?

Discussion in 'Homework Help' started by acamarujin, Oct 20, 2015.

  1. acamarujin

    Thread Starter New Member

    Oct 20, 2015
    1
    0
    I found 2 equations for dynamic resistance of a diode and I want to know the difference between them
    1.
    Rd=KT/q(I+Is)
    2.
    rd=nVT/IdQ

    I just started learning about analog electronics in college and I couldn't find anything that it's complementary to my courses
    For example I couldn't find anything about Small-signal equiv circuit
    and if I could find some solved problems it will be wondeful
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,748
    4,796
    Use the notion that, around a particular large-signal operating point, Vo and Io, the instantaneous voltage and current, v(t) and i(t), can be written as the sum of the large-signal values and the small-signal values:

    v(t) = Vo + Δv(t)
    i(t) = Io + Δi(t)

    For sufficiently small deviations from the large-signal operating point, the relationship between Δv(t) and Δi(t) can be approximated as being linear such that

    Δv(t) = rd·Δi(t)

    To find rd, simply start with the basic constitutive equation for a p-n junction diode and apply the above notion.
     
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