Simple noise formulas for MOS analog design

The designer needs simple and accurate models to estimate noise in MOS transistors as a function of their size, bias point and technology. In this work, we present a simple, continuous, physics-based model for flicker noise. We review also thermal noise and we examine the behavior of the corner frequency (f_c) in terms of the bias point. The expressions that are presented are simple and valid in all the operating regions, from weak to strong inversion, constituting a useful set of equations for low noise analog design. Finally we examine the design of two low noise circuit elements, fabricated in a 0.8μm technology.