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 100 dB and the total power consumption is less than 30 mW. 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 100 dB and the total power consumption is less than 30 mW.