Design of CMOS readout frontend circuit for MEMS capacitive microphones

This paper deals with a frontend part of the readout circuit developed as an integrated circuit that after bonding together with a MEMS capacitive microphone (MCM) chip will be used in a noise dosimeter applicable in very noisy and harsh environment, e.g. mine. Therefore, the main attention has been paid to the high dynamic range, low offset and low noise of the developed readout interface as well as its low- power consumption feature. For conversion of the MCM’s capacitance variation into voltage, an approach based on the buffered input conversion stage biased by a voltage divider was used. The advantage of this approach is that the voltage divider formed by MOS transistors can be connected to the high-impedance node (i.e. the output of the MCM, in this case). The whole frontend part of the readout interface was designed in a standard 0.35mm CMOS technology. Finally, the achieved results are discussed and compared to other works