Oversampling A-to-D and D-to-A converters with multistage noise shaping modulators

High-resolution oversampling analog-to-digital-to-analog converters are proposed. The converters utilize multistage noise shaping modulation techniques that can be implemented with VLSI MOS technology. The modulators consist of multiconnected single-integration delta-sigma modulation loops. Quantization noise in the first delta-sigma loop is requantized by the next delta-sigma loop and cancelled by adding the requantized noise to the first-stage signal. Quantization noise in the modulated signal is suppressed by double or multiple integration gain. Modulator resolution increases with the number of stages without feedback loop instability problems. A three-stage multistage noise shaping modulator with 1-bit quantization achieves the equivalent of 16-bit resolution for the hi-fi audio band at 2-MHz sampling rate. Simulation results show that analog-to-digital and digital-to-analog converter circuits constructed of switched capacitors do not require highly accurate components.<
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