A Simple Model for the Thermal Noise of Saturated MOSFETs at All Inversion Levels

We propose a single formula for the channel thermal noise of saturated long-channel MOSFETs operating in weak, moderate, and strong inversion. Our approach is based on a novel interpolation of well-known analytical formulas known to be valid in weak and strong inversion, and the result is both accurate and simple enough to be useful for hand calculations. We expect the formula to be particularly useful for designing energy-efficient analog circuits biased in moderate inversion. We have validated it using noise measurements of nMOS and pMOS transistors in a 0.5-μm CMOS process.