small-signal impedance

As equations (10.2) clearly demonstrate, the small-signal impedance of a nonlinear network depends on its operating bias.

The small-signal impedance at DC (frequency of 0) is the same as the resistive component of the impedance and is termed output resistance.

In circuit design, an active load is a circuit component made up of active devices, such as transistors, intended to present a high small-signal impedance yet not requiring a large DC voltage drop, as would occur if a large resistor were used instead.