Ultra low-power low-noise transimpedance amplifier for MEMS-based reference oscillators

A transimpedance amplifier (TIA) has been designed in a 130 nm CMOS technology node to serve as a sustaining amplifier for a MEMS-based oscillator. A regulated cascode (RGC) configuration is used at the input stage to reduce the impact of the input parasitic capacitance on the TIA bandwidth as well as to minimize loading effects on the Q-factor of the resonator. In typical conditions, the TIA achieves a mid-band gain of 112.5 dBΩ and a 3 dB bandwidth of 239 MHz, while dissipating only 360 μW from a 1.2V supply. A linear RLC model of a MEMS wine-glass disk resonator resonating at 20 MHz with a Q-factor of 10⁴ is used to validate the TIA. The post layout simulations show a phase noise below -125 dBc/Hz at a 1 kHz offset and a noise floor of -131.9 dBc/Hz.