A Sub-mW 18-MHz MEMS Oscillator Based on a 98-dBΩ Adjustable Bandwidth Transimpedance Amplifier and a Lamé-Mode Resonator

Abstract

This paper presents a microelectromechanical system (MEMS)-based oscillator based on a Lamé-mode capacitive micromachined resonator and a fully differential high-gain transimpedance amplifier (TIA). The proposed TIA is designed using TSMC 65 nm CMOS technology and consumes only 0.9 mA from a 1-V supply. The measured mid-band transimpedance gain is 98 dBΩ and the TIA features an adjustable bandwidth with a maximum bandwidth of 142 MHz for a parasitic capacitance CP of 4 pF. The measured input-referred current noise of the TIA at mid-band is below 15 pA/Hz−−−√. The TIA is connected to a Lamé-mode resonator, and the oscillator performance in terms of phase noise and frequency stability is presented. The measured phase noise under vacuum is −120 dBc/Hz at a 1-kHz offset, while the phase noise floor reaches −127 dBc/Hz. The measured short-term stability of the MEMS-based oscillator is ±0.25 ppm.