Supporting circuitry for a fully integrated micro electro mechanical (MEMS) oscillator in 45 nm CMOS technology

Two oscillator circuits designed in 45 nm technology incorporating an integrated capacitive vibrating Micro Electro Mechanical (MEMS) resonator for microprocessor applications are presented. The general topology of the oscillator is based on a shunt-shunt feedback transimpedance amplifier with an automatic gain control circuit to ensure linear operation of the integrated resonator to reduce the oscillator 1/f³ phase noise component introduced by the resonator nonlinear capacitive transducer. Two different topologies for the transimpedance amplifier are presented: the first topology uses a self biased fully differential amplifier while the second topology uses a multi stage gm-boosting amplifier with a negative feedback amplifier for self biasing. The designed circuits operate robustly across all process corners and across 120°C temperature range from -10°C to 110°C while consuming less than 8 mW power and occupying an area of 300um×255um and phase noise of -120dBC/Hz at 200KHz offset. The designed circuits are the first implementation of a MEMS based oscillator in deep submicron processes showing robust performance across all process corners and variations.