A 1-V, 1-MS/s, 88-dB sigma-delta modulator in 0.13-μm digital CMOS technology

A low-voltage switched-capacitor fourth-order Σ-Δ modulator using full feed-forward is introduced. It has two advantages: the unity signal transfer function and reduced signal swings inside the Σ-Δ loop. These features greatly relax the DC gain and output swing requirements for OTAs in the deep submicron CMOS Σ-Δ modulator. With careful signal scaling, signal swings inside the loop can be suppressed to less than 50% of the reference voltage, which is highly desirable by low-voltage designs. Implemented by a 0.13-μm pure digital CMOS technology, the Σ-Δ modulator achieves 1-MS/s conversion speed and 88-dB DR with 7.4-mW power dissipation under 1.0-V power supply voltage.