A Fully Differential Comparator-Based Switched-Capacitor $\Delta\Sigma$ Modulator

In this brief, a fully differential comparator-based switched-capacitor (CBSC) second-order delta-sigma (DeltaSigma) modulator is presented. To ensure differential operation, the CBSC DeltaSigma modulator utilizes a common-mode feedback circuit to balance the pull-up current and the pull-down current in the ramp generator. This modulator has been fabricated in a standard 0.18-mum CMOS process. The active area is 0.21 mm
²
, and the power consumption, excluding output buffers, is 0.42 mW from a 1.8-V supply. This modulator achieves 65.3-dB signal-to-noise-plus-distortion ratio and an input dynamic range of 71 dB when sampled at 2.56 MS/s (OSR = 64).