A low-power high dynamic-range sigma-delta modulator for a capacitive microphone sensor

An opamp time-multiplexed topology of a third- order SigmaDelta modulator is presented in this paper. This topology implements a third-order noise transfer-function using only two opamps by sharing one opamp between second and the third integrators of the modulator. The simulated results are comparable to a low-power modulator with three separate opamps. The proposed SigmaDelta modulator is designed for a silicon microphone front-end. In the audio-band (20-20 kHz), it features a dynamic range above 80 dB, consuming 90 muWatts with a supply voltage of 1.8 V.