1/f NOISE IN LARGE SIGNAL OPERATION OF PASSIVE COMPONENTS

Abstract

A model for the 1/f noise in large signal operation of linear passive one-port (e.g. carbon or polysilicon resistors) is given. Starting from the Hooge's formula, that holds when the component is operated under DC bias, it is shown that the noise current is simply proportional to the product between the conductivity fluctuation and the time-dependent large signal applied to the component. Otherwise stated, the 1/f noise exhibited by passive components in large signal operation arises from the intermodulation between the stochastic process "conductivity fluctuation" and the signal applied to the component. Detailed calculations of both autocorrelation function and power spectrum of the resulting noise current are given; different time dependence of the signal applied to the component are considered. Of particular relevance in practical applications is the case of sinusoidal signal plus an eventual DC bias; in this case the resulting noise current is a cyclostationary stochastic process, and its behaviour can be conveniently described by the cyclic autocorrelation functions or by the cyclic power spectra. The measured power spectra of the noise current of carbon resistors with DC bias and large periodic signal applied to them, are in good agreement with those calculated from the proposed model. The agreement of the measured power spectra with those predicted by the model allows to conclude that the physical origin of 1/f noise in passive components does not depend on the applied bias, DC or large signal alternating, since, in any case, the noise current is conveniently modeled by intermodulation (product) between the "conductivity fluctuation" stochastic process and the applied signal.