Design for optimum performance-to-power ratio of a continuous-time Σ Δ modulator

Low-power is a key issue in designing A/D converters for battery powered applications like cellular phones. A continuous-time ΣΔ modulator is well suitable for these applications [1] because of its low-power consumption, which is mainly determined by the noise and distortion requirements. In this paper the relation between power of the input stage and distortion of a continuous-time base-band ΣΔ modulator is analysed. As noise and distortion requirements of the first stage are most stringent, its contribution to the total power consumption of the ΣΔ modulator is dominant. From the theoretical results, a strategy for designing a low-power and high performance ΣΔ modulator is determined. Using this strategy a low-power low-distortion 4th-order ΣΔ modulator has been designed.