Very low frequency cyclostationary 1/f noise in MOS transistors

Cyclostationary operation of the MOS transistor has been proposed in recent years as a technique for reducing the flicker noise at the device level itself. Several works report measured cyclostationary flicker noise reduction, the PSD showing a plateau below the switching frequency, but at much lower frequencies the slope resembles again the original 1/f spectrum. But current models do not correctly address the latter effect. In this work, the PSD of a DC biased transistor is first deduced using only Shockley-Read-Hall (SRH) statistics and the autocorrelation formalism. Then the analysis is extended by means of simulations and using reasonable physical hypotheses, to a cyclostationary bias condition. The results allow explaining reported experimental data in the whole frequency range. Finally the development of a specific integrated circuit aimed at switched flicker noise measurements in different types/sizes of test transistors and at different bias conditions is presented.