Created at: 2025-02-02
We often deal with electronic devices for which I is not proportional to V ;
in such cases there’s not much point in talking about resistance, since the
ratio V /I will depend on V , rather than being a nice constant, independent
of V . For these devices it is sometimes useful to know instead the slope of
the V –I curve, in other words, the ratio of a small change in applied
voltage to the resulting change in cur- rent through the device, ΔV /ΔI (or
dV/dI). This quantity has the units of resistance (ohms) and substitutes for
re- sistance in many calculations. It is called the small-signal resistance,
incremental resistance, or dynamic resistance.
(The art of electronics 3rd ed.).
Zener diodes are an example of the above.