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 chopperstabilization (CHS), while SF buffer shields the MCM sensor from the switching spurs. The PAMP uses Mil 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 950~m x 950~ in O.35~m CMOS technology and draws a 50~ total current from a 1.8V single supply. The PAMP achieves SNDR of 44dBAlPa (elec. meas.) and 27dBAlPa (acoustic meas.) and a conversion range from 50dBSPL to 120dBSPL.
A multifunctional low-power preamplifier for MEMS capacitive microphones
Gottardi, Massimo;Baschirotto, Andrea;
2009-01-01
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 chopperstabilization (CHS), while SF buffer shields the MCM sensor from the switching spurs. The PAMP uses Mil 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 950~m x 950~ in O.35~m CMOS technology and draws a 50~ total current from a 1.8V single supply. The PAMP achieves SNDR of 44dBAlPa (elec. meas.) and 27dBAlPa (acoustic meas.) and a conversion range from 50dBSPL to 120dBSPL.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
