A 164-dBΩ Transimpedance Amplifier for Monolithic CMOS-MEMS Oscillators in Biosensing Applications

This article presents a fully differential tunable high-gain transimpedance amplifier (TIA) conceived as a front-end circuit for monolithic CMOS-MEMS resonators operating in self-sustained oscillation mode. The proposed solution is based on a capacitive-feedback network topology by means of a varactor for gain control. The design is specifically oriented to CMOS-MEMS biosensing applications that require post-CMOS MEMS processing since the adoption of a TIA solution provides robustness against one of such processing steps (i.e., oxygen plasma activation) and a 10\times improvement in feedthrough signal elimination compared to a single-ended alternative. The ASIC was fabricated using a 0.35- \mu m commercial CMOS technology from Austria Microsystems featuring a maximum transimpedance gain of 164 dB \Omega with a 10-dB tuning range. It operates at frequencies up to 10 MHz with an input-referred current noise density as low as 13 fA \cdot Hz ^{\mathrm {-1/2}} providing an exceptional high-performance sensing. With a 3.3 V supply voltage, it exhibits a 1.6 mW power consumption. The TIA was integrated on-chip with various MEMS resonator topologies, either oriented to volatile organic compounds (VOCs) detection or to microfluidics integration for Lab-on-Chip (LoC) systems, corroborating self-sustained oscillation with a 135-ppb measured Allan deviation and 1.1 V output voltage swing.