A low-complexity low-distortion topology for wideband delta-sigma ADCs

In wideband applications, ΔΣ analog-to-digital converters have to use lower oversampling ratio (OSR) due to technology limits. Higher-order modulators and/or multibit quantization/feedback therefore are utilized to compensate the corresponding signal-to-noise-ratio (SNR) loss, which consequently leads to a significant increase in hardware complexity, chip area and power dissipation. Low OSR also increases the ADC´s sensitivity to circuit imperfections, which in turn, requires building blocks with higher specifications. In this paper, we present a topology that significantly reduces both the complexity of multibit quantization and the ADC´s sensitivity to nonlinear multibit quantization. It can also be used with other low-distortion techniques to reduce total nonideal effects. A technique that reduces the DAC complexity is also proposed.