Thermal noise in nonlinear resistive devices and its circuit representation

Major developments in the study of thermal noise in linear and nonlinear dissipative devices since the Nyquist theorem are summarized. A recently established theorem for calculating thermal noise in biased, near-equilibrium, nonlinear devices is presented, giving assumptions and approximations necessary for performing the derivation. Examples of the use of the theorem are presented, and an equivalent circuit model for representing the noise in the above devices is proposed, based on the theorem. This model is applied to analyze the behavior of nonlinear resistors of these in such applications as refrigerators and heat engines. This model shows that a nonlinear resistor cannot serve as Maxwell's demon, and has allowed the solution of several problems, and may have applications for furthr problem solving.