A 5.35-mW 10-MHz Single-Opamp Third-Order CT $\Delta\Sigma$ Modulator With CTC Amplifier and Adaptive Latch DAC Driver in 65-nm CMOS

This paper reports a continuous-time (CT) third-order delta-sigma modulator that features a single amplifier biquad (SAB) and a passive integrator to simplify the circuit to just one power hungry operation amplifier (opamp). Such setup not only relaxes the gain and bandwidth requirement of the opamp design but also enhances the overall modulator stability which enables a power-efficient loop filter implementation. We used an SAR architecture in the quantizer with an advanced feedback technique to alleviate its speed penalty. By incorporating the proposed CT complementary (CTC) opamp and an adaptive latch scheme in the DAC driver, the modulator attains a signal bandwidth of 10 MHz with 79.6-dB signal-to-noise and distortion ratio (SNDR) while only consuming 5.35 mW from 1.2- and 1.8-V power supplies. The prototype has a dynamic range of 84.5 dB and a Schreier FoM of 177.2 dB with an active area of 0.033 mm
²
.