Amplitude and Phase Noise in Modern CMOS Circuits

Understanding noise in submicron MOS devices is an ongoing challenge in the area of mixedsignal modeling. Experimental observations show that the classical long-channel MOSFET noise formulation underestimates the drain current noise of short-channel devices by a factor often referred to as the excess noise factor. The numerical value of this factor is still a matter of controversy, raising questions regarding the future of CMOS analog design. In order to predict the effects of this excess noise on amplitude and phase noise in future CMOS circuits, it is crucial to have a reliable MOSFET noise model and an accurate phase noise formulation. In this dissertation we first present the semi-ballistic MOSFET noise model which is based on the transport properties of ballistic MOSFETs. Unlike most existing models, this model is not based on the long-channel formulation. Thus it does not require continual revision as we discover emerging short-channel effects. We first show that the dominant physical phenomenon responsible for noise in ballistic devices is the shot noise generated by the potential barrier next to source. We then use results of historic studies on vacuum tubes to show that noise in short-channel MOSFETs is partially-suppressed shot noise. Using this model, we study the overall noise performance of future MOSFETs and discuss its implications for the future of circuit and device engineering for analog applications. We then discuss the effects of device noise on phase noise of electrical oscillators and present the time-domain formulation of phase noise, a method that is especially accurate for switchingbased oscillators. The advantage of having an accurate phase noise formulation is twofold. It can be used to predict phase noise for a given device noise level and to calculate the device noise from phase noise measurements. The latter application is called indirect device noise characterization through phase noise measurement, a method that we introduce in this work. The time-domain phase noise formulation can also be used to investigate the properties of phase noise, especially at close-in frequencies. We explore all of these applications. To validate our semi-ballistic MOSFET noise model we use detailed hydrodynamic device sim-