Theory of thermal noise in long-channel MOS transistors operating before saturation

Abstract

This article reports a reinvestigation of the existing thermal noise theory for long-channel MOS transistors, which is shown to have serious flaws as a thermal noise theory. We conclude that the spectral intensity of the channel thermal noise current for a long-channel MOSFET, operating before saturation at both strong and weak inversions, is best given by applying a new theory, which we refer to as the steady-state Nyquist theorem for one-dimensional devices. We also show that a general three-dimensional approach for calculation of the short-circuit thermal noise currents in semiconductor devices supports the new theory. Clear and definitive experimental evidence in support of the steady-state Nyquist theorem is provided.