The study of CMOS based VCO with active inductor and its design methodology

Active Inductors are useful in reducing the large chip area typically consumed by spiral inductors, as well as providing larger inductance values and higher quality factors that otherwise cannot be achieved by spiral inductors. Integrated inductors find application in many radio frequency (RF) front end integrated circuits, including impedance matching, filtering, biasing and in oscillator circuits. Nonetheless, because of the interdependent relationship of the self-resonant frequency and quality factor it is often difficult to meet desired circuit requirements. Additionally, active devices pose problems of higher power consumption , noise figure and potential instability. This thesis begins with the study of active inductors, the Wu active inductor in particular, and considers tuning methods based on the Wu active inductor topology. Starting with the small-signal model, the emulated inductance and quality factor expressions are derived. Next, the operation of active inductors under large-signal is closely examined. Comparisons between a passive and an active VCO are made. The active inductor based voltage-controlled oscillator (Active VCO) is studied extensively, and the methods of improving the performance under large signal-behavior are discussed. Then a design procedure based on gm/ID methodology is proposed. A Matlab script that can be applied to gyrator-C based active inductors is developed to determine the sizing of the transistors for a desired inductance and resonant frequency. Cadence Virtuoso is used for simulations, and extraction based on an IBM 8RF technology file. Finally, a low power active VCO is designed, simulated and laid out.M.S.Includes bibliographical referencesby Sy-Min Chuen