In this contribution, we review the use of physical models for the noise simulation of devices operated in nonlinear
conditions, thus requiring a full mixed-mode simulation of the device and of the embedding circuit. After
presenting a detailed formulation of the model, we discuss two significant case studies: a downconversion GaAs
MESFET mixer, and a detailed analysis and physical interprettion of low-frequency noise upconversion in a pn
This contribution is aimed at describing the available techniques for simulating trap-assisted generation recombination noise in electron devices. We consider physics-based models, where carrier transport equations are complemented by a set of rate equations, one for each trap energy level included in the model, expressing charge conservation. To the aim of noise analysis, such rate equations include stochastic Langevin sources representing level occupancy fluctuations, whose statistical properties are known from basic physical analysis. A generalization of the standard Green's function technique to the physics-based noise analysis can be then exploited to propagate the internal fluctuations to the device terminals, in order to evaluate the correlation matrix of the external noise generators. With reference to a simple device, a superposition of noninteracting trap levels with a proper distribution of timeconstants is shown to yield a 1/f spectrum on a prescribed frequency range.
In large-signal operation the fundamental white noise fluctuations are amplitude modulated by the periodic device working point and converted into cyclostationary fluctuations. The cyclostationary internal noise is then propagated to the device terminals by means of proper Green's functions that also involve noise frequency conversion. The same device discussed in small-signal operation is simulated in cyclostationary conditions, therefore demonstrating the upconversion of 1/f noise from baseband to the steady-state harmonics.
The paper reviews the physics-based approach to the frequency conversion and noise analysis of semiconductor devices operating in forced large-signal (quasi) periodic regime. Noise analysis under large-signal operation is presented as a direct extension of the classical physics-based noise simulation technique where the modulated microscopic noise sources are propagated to the external device terminals through Green's functions. A complete discussion of a simple yet significant case study is presented with reference to a junction diode, which allows for an analytical cyclostationary noise model. To complete the paper, we include an analysis of the validity of two widely exploited approximated system-oriented cyclostationary noise modelling approaches, based on the modulation of small-signal stationary noise spectra.
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