This paper presents an oscillator based on a fully differential adjustable-bandwidth transimpedance amplifier (TIA) and a piezoelectric micromachined bulk-mode disk resonator. The TIA includes a regulated cascode stage and a common source active feedback topology. The TIA is designed in 65-nm CMOS and consumes 1.4 mA from a 1-V supply. The measured maximum mid-band transimpedance gain is ~80 dBQ and the TIA features an adjustable bandwidth of up to 214 MHz, when driving a shunt parasitic capacitance C _P of 4 pF. The measured input-referred current noise of the TIA at mid-band (i.e., ~20 kHz-40 MHz) is below 3.7 pA/√Hz. The TIA is connected with the disk resonator in [1], and the oscillator performance in terms of phase noise and frequency stability is reported. The measured phase noise in air and under vacuum, at a 1-kHz offset, is -104 and -116 dBc/Hz, respectively. The close-to-carrier phase noise is also low in air and under vacuum with -40 and -60 dBc/Hz, respectively, at a 10-Hz offset, while the far-from-carrier phase noise reaches -130 dBc/Hz. The measured short-term stability of the MEMS oscillator is of ±0.38 ppm.

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 dB $\Omega$ and the TIA features an adjustable bandwidth with a maximum bandwidth of 142 MHz for a parasitic capacitance $C_P$ of 4 pF. The measured input-referred current noise of the TIA at mid-band is below 15 pA/ $\sqrt{\mathrm{Hz}}$ . 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.

This paper presents a Verilog-A model of a microelectromechanical systems (MEMS) clamped-clamped beam resonator. The model captures the electrical and mechanical non-linear effects, and accounts for the spring softening and Duffing behavior present in resonators at high drive levels. A transimpedance amplifier is designed in 0.13μm CMOS to implement and simulate a MEMS-based oscillator incorporating the Verilog-A model. The phase noise performance dependance on the resonator non-linear effects and its bias voltage are illustrated through simulations. Simulation results confirm that careful design must be applied when MEMS resonators are utilised in order to ensure that non-linearities and biasing do not significantly deteriorate oscillator performance.