Noise-Coupled .DELTA..SIGMA.AD Modulator with Shared OP-Amp

Abstract

This paper proposes an improved architecture of the noise-coupled ΔΣAD modulator with OP-Amp sharing technique. The noise-coupled ΔΣAD modulator enhances the order of noise-shaping efficiently by adding some passive capacitors and switches. However, in a conventional noise-coupled ΔΣAD modulator with feedforward path, an analog adder is needed before the quantizer, and especially in a multibit modulator, an additional amplifier is necessary to realize the summation of feedforward signals and coupled quantization noise, which leads to extra chip area and power dissipation. In this paper, we propose a novel architecture of the noise-coupled ΔΣAD modulator with OP-Amp sharing technique, which realizes the summation of feedforward signals and coupled quantization noise without an additional amplifier. The proposed architecture is functionally equivalent to the conventional noise-coupled modulator with smaller chip area and low power dissipation. We have performed simulation with MATLAB and SPICE to verify the effectiveness of the proposed architecture and modulator circuits. The simulation results show that the proposed modulator can realize the noise-shaping enhancement effectually as the same as the conventional noise-coupled modulator with small overhead.