A Delta Sigma-Modulated Sample and Average Common-Mode Feedback Technique for Capacitively Coupled Amplifiers in a 192-nW Acoustic Analog Front-End

This work presents an acoustic analog front-end based on a delta sigma-modulated sample and average common-mode feedback technique. The proposed feedback offers a process and temperature stable high pass (HP) frequency corner, unity dc feedback gain, and a programmable HP frequency corner to reduce startup time. In addition, this article also presents an automatic saturation detection and recovery technique from in-band input artifacts. The proposed technique was implemented in the low-noise amplifier (LNA) and programmable gain amplifier (PGA) of an acoustic analog front-end fabricated in 180-nm CMOS. The technique achieved a maximum effective resistance of 100 T omega . The HP frequency corner variation across temperature and process was reduced by 226x and 4.38x, respectively, compared to a traditional pseudo-resistor feedback structure. Integrated noise in the 20 Hz-4 kHz speech signal band is reduced by 2.98x using the lowest possible HP frequency corner. The amplifier recovery time from saturation due to artifacts was reduced by 10x. The total power consumption of the LNA, PGA, and analog to digital converter (ADC) in the acoustic front-end was 192 nW.