An ultra-efficient recycling folded cascode OTA based on GAA-CNTFET technology for MEMS/NEMS capacitive readout applications

This paper demonstrates an ultra-efficient recycling folded cascode (RFC) operational transconductance amplifier (OTA) as one of the cardinal blocks in most analog microsystems. Two positive feedbacks are utilized in the proposed RFC OTA to enhance the input transconductance and the output impedance. All GAA-CNTFETs are biased in the near-threshold region (V_T≈0.37 V and V_DD=±0.2 V) to reduce power consumption. The simulation results indicate that with C_Load = 5pF, the proposed RFC OTA shows 102 dB open-loop gain and 17.2 MHz unit gain-bandwidth with an ultra-low power consumption of 111.5nW and a reasonable slew rate response (17.3 V/µs). A capacitive readout circuit for micro-and nano-electromechanical systems (MEMS/NEMS) applications is suggested to assess the proposed RFC OTA's performance in practical applications. By utilizing an RC sensing feedback structure, the proposed transimpedance amplifier presents 155dBΩ gain with a 400 MHz bandwidth. Compared to the other counterparts, the proposed GAA-CNTFET-based TIA presents fascinating power savings 86% total average improvement) and 1.6 times total average gain improvement. Our simulation results accentuate that the proposed GAA-CNTFET-based RFC OTA is a powerful candidate for designing ultra-efficient MEMS/NEMS capacitive accelerometers readout circuits.