On May 25, 3:30*am, Owen wrote:
If the circuit is not linear in those terms, then you cannot form a
valid Thevenin equivalent circuit, and discussion of the Thevenin
equivalent series source impedance is a nonsense... it cannot be used.

Quoting "Fields and Waves ...", by Ramo and Whinnery, "... the
(Thevenin) equivalent circuit was derived to tell what happens *IN THE
LOAD* under different load conditions, and significance cannot be
automatically attached to a calculation of power loss in the internal
impedance of the equivalent circuit."
--
73, Cecil, w5dxp.com