A multi-function two-stage chopper-stabilized preamplifier (PAMP) for MEMS capacitive microphones (MCM) is presented. The PAMP integrates digitally controllable gain, high-pass filtering and offset control, adding flexibility to the front-end readout of MCMs. The first stage of the PAMP consists of a source-follower (SF) while the second-stage is a capacitive gain stage. The second-stage employs chopper-stabilization (CHS), while SF buffer shields the MCM sensor from the switching spurs. The PAMP uses MΩ poly bias resistors for the second-stage, exploiting Miller effect to achieve flat audio-band response. The gain and high-pass filtering corner can be adjusted by digitally controlling the capacitor banks in the PAMP. The offset-control feature of the PAMP is implemented using a narrow-band low-pass gm-C filter. The PAMP occupies 950μm x 950μm in 0.35μm CMOS technology and draws a 50μA total current from a 1.8V single supply. The PAMP achieves SNDR of 44dBA/Pa (elec. meas.) and 27dBA/Pa (acoustic meas.) and a conversion range from 50dBSPL to 120dBSPL. © 2009 IEEE.
Jawed, S., Nielsen, J., Gottardi, M., Baschirotto, A., Bruun, E. (2009). A multifunction low-power preamplifier for MEMS capacitive microphones. In ESSCIRC, 2009. ESSCIRC '09. Proceedings of (pp.292-295) [10.1109/ESSCIRC.2009.5325947].
A multifunction low-power preamplifier for MEMS capacitive microphones
BASCHIROTTO, ANDREA;
2009
Abstract
A multi-function two-stage chopper-stabilized preamplifier (PAMP) for MEMS capacitive microphones (MCM) is presented. The PAMP integrates digitally controllable gain, high-pass filtering and offset control, adding flexibility to the front-end readout of MCMs. The first stage of the PAMP consists of a source-follower (SF) while the second-stage is a capacitive gain stage. The second-stage employs chopper-stabilization (CHS), while SF buffer shields the MCM sensor from the switching spurs. The PAMP uses MΩ poly bias resistors for the second-stage, exploiting Miller effect to achieve flat audio-band response. The gain and high-pass filtering corner can be adjusted by digitally controlling the capacitor banks in the PAMP. The offset-control feature of the PAMP is implemented using a narrow-band low-pass gm-C filter. The PAMP occupies 950μm x 950μm in 0.35μm CMOS technology and draws a 50μA total current from a 1.8V single supply. The PAMP achieves SNDR of 44dBA/Pa (elec. meas.) and 27dBA/Pa (acoustic meas.) and a conversion range from 50dBSPL to 120dBSPL. © 2009 IEEE.
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