A Single Op-Amp Resonator-Based Continuous-Time Sigma–Delta Modulator With Time-Division Switching for Excess Loop Delay Compensation

This brief presents a time-division switching (TDS) technique aimed at excess loop delay (ELD) compensation for a continuous-time sigma-delta modulator (SDM) based on a third-order single op-amp resonator (SOR). By reconfiguring the transfer function of the SOR with the clock signal, the proposed method achieves ELD compensation, resulting in improved power and area efficiency, as well as enhanced immunity to non-idealities. The proposed SDM is implemented using a single amplifier to realize a third-order resonator, and it employs a single feedback digital-to-analog converter using the proposed TDS ELD compensation method. The modulator, which occupies only 0.094 mm2 of the active area, was fabricated in a 180-nm CMOS technology. It consumes 100-
$\mu \text{W}$
power from a 1.8-V supply, and it achieves a peak signal-to-noise and distortion ratio of 63.8 dB and a dynamic range of 65.2 dB in a 400-kHz signal bandwidth when clocked at 40 MHz. The proposed method offers a simple and attractive solution for ELD compensation in third-order SOR-based SDMs.