TABLE OF CONTENTS This chapter deals with the fundamental noise in MOS transistors. The fundamental noise of a device is the result of the spontaneous fluctuations in current and voltage inside the device that are basically related to the discrete nature of electrical charge. Fundamental noise imposes limits on the performance of amplifiers and other electronic circuits. In contrast to pickup noise, that can be reduced or eliminated by appropriate shielding, fundamental noise cannot be eliminated because it is created in the device itself.
The study of noise in MOS transistors [1], [2] began shortly after the basic dc modeling had been carried out [3], [4] and was preceded by the study of noise in junction field-effect transistors [5], [6].
This chapter begins with a short summary of the various sources of noise. The impedance field method for calculating noise in devices is then introduced, and the fundamental thermal and flicker noise models are developed. Later, the basic requirements for a consistent noise model of the MOS transistor are given and design-oriented noise models are presented. Finally, small dimension effects on noise are considered.
Thermal noise is present in thermal equilibrium (in the absence of current) in any resistor. This is due to the fact that the electrons collide randomly with the thermally agitated atoms of the resistor. The effect is similar to the Brownian movement of particles suspended in a liquid analyzed by Einstein in 1905 [7]. Brownian movement is basically explained by the...
