Abstract: Piezoelectric MEMS (pMEMS) microphones are suitable for low-power applications, as the sensing element is passive, eliminating the need for a charge pump to bias the microphone. Furthermore, the inherent robustness to dust and moisture eliminates the need for a protective mesh cover used in the commercially available capacitive MEMS (cMEMS) microphones. However, the pMEMS element has a high-impedance capacitive source (reaching several GOhm at low audio frequencies), so the interface circuit’s input node is weakly driven, making it sensitive to dc leakage currents, parasitic capacitance, and current noise sources. Furthermore, commonly used techniques such as chopping and auto-zeroing to mitigate flicker noise do not work well when interfacing a high-impedance input source. This work analyzes the fundamental constraints and the impending challenges of interfacing a high-impedance capacitive source using a pMEMS microphone as a representative case study. Practical guidelines for achieving low noise and low power are presented. Two types of analog front-end (AFE) architectures are implemented: (a) open-loop AFE’s for low power and relaxed resistive load support (25 kOhm), and (b) closed-loop AFE’s for driving heavy loads (2 kOhm). Four AFEs are implemented and taped out with JFET and pMOS-input variants for comparative characterization of the input DC leakage and current noise performance. Measurement methodologies for emulating the pMEMS microphone and performing input DC leakage and input-referred current-noise measurements are presented. Simulations reveal that the proposed AFEs match the performance level of commercial analog-output cMEMS microphones while targeting a sub-1 dBA SNR degradation and low current consumption.

Event Details
Title: Design of analog front ends for a piezoelectric MEMS microphone
Date: February 25, 2026 at 3:00 PM
Venue: ESB 234
Speaker: Mr. CHETAN SHIVALINGAPPA RAJENAVAR (EE23S039)
Guide: Dr. Nagendra Krishnapura
Type: MS seminar

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