Optimizing MOSFET channel width for low phase noise in LC oscillators

Phase Noise is an important consideration in oscillators. A procedure to obtain low phase noise through MOSFET channel width optimization is described in this paper. The impact of channel width is different for white and flicker noise. The Phase Model used for this purpose is based on a circuit based model. While the Phase Noise due to white noise increases with channel width increase, that due to flicker noise decreases, thereby setting up the conditions for optimization. We derive mathematically that optimum channel width that results in the lowest phase noise with other parameters remaining constant and verify our results by simulation.