A 100dB-SNR mixed CT/DT audio-band sigma delta ADC

Although audio-band sigma delta ADC has largely been implemented as discrete time circuits, a continuous time approach offers significant advantages for high accuracy low-power applications. A continuous time design allows for relaxed amplifier unity-gain bandwidth and power requirements. It also provides better noise immunity due to their inherent anti-aliasing properties. This paper introduces a mixed continuous-time/discrete- time, single-loop, fourth-order, 4-bit audio-band sigma delta ADC that combines the benefits of continuous time and discrete time circuits, while mitigating the challenges associated with continuous time design. Measurement results show that the peak SNR of this ADC reaches 100dB and the total power consumption is less than 30mW.