On the high frequency excess noise and equivalent circuit representation of the MOS-FET with n-type channel

Abstract

The noise in MOS-FET's is here represented by four parameters: the equivalent noise resistance R n (measuring the drain noise), the equivalent noise conductance g n (measuring the uncorrelated part of the gate noise) and the correlation admittance Y z = g z j ωC z (measuring the correlated part of the gate noise). For some large geometry units we compared the experimental values of these parameters with the ones calculated under the assumption that the noise in the channel was thermal noise. Serious discrepancies between the theoretical and the experimental values were noted, indicating that white noise of non-thermal origin must be present in the channel. The observed data are explained with the help of local “mobility fluctuations” in the channel. By making reasonable assumptions about this noise source, the observed data can be explained in a qualitative manner.