Link between Continuous and Discrete Descriptions of Noise in Nonlinear Resistive Electrical Components

We consider the modeling of noise in a nonlinear, classical, resistive electrical component using two models: i) a continuous description based on a stochastic differential equation with a white thermal Gaussian noise; ii) a discrete, shot noise model based on a Markovian master equation. We show that thermodynamics imposes in i) the use of the H\"anggi-Klimontovich (H-K) prescription when the noise depends on bias voltage, and implies a generalized Johnson-Nyquist relation for the noise where the conductance is replaced by the ratio mean current over voltage. In ii) we show that the discrete description compatible with thermodynamics leads to the continuous one of i) with again the H-K prescription. Here the generalized Johnson-Nyquist relation for noise is recovered only at low voltage, when the continuous description is valid.