A Low Power, Low Distortion Single-bit Sigma-Delta Audio DAC with Distributed Feedback from Analog Output

A single-bit low power, low-distortion digital-to-analog converter (DAC) using distributed feedback structure for low output impedance audio application is presented. The current structure is a modified forth-order inversed follow-the-leader feedback (IFLF) emphasizing on achieving high system performance with much reduced power consumption. This structure utilizes the distributed feedback from analog output to attenuate the nonlinear distortions from both the discrete time to continuous time interface and the output stage, and finite-impulse response (FIR) filter to attenuate the out-band quantization noise. The power consumption is reduced by the class-AB operation in the last stage OTA design. Systematic comparisons of the performance and power consumption are simulated by both Cadence and Matlab/Simulink. The results indicate that the proposed structure can achieve high SNDR with very low power consumption. Typically, the distortion can be attenuated at least by 95dB at 5 KHz input. To compare different DAC designs, the new Figure of Merit (FOM) is introduced and the current design shows significant improvement comparing the results in the literature. This proposed structure will be potentially useful for low-impendence low-power audio applications.