A 1.2-V 0.18-${\mu}m$ Sigma-Delta A/D Converter for 3G wireless Applications

A low-voltage switched-capacitor $2^{nd}$-order $\Sigma\Delta$ modulator using full feed-forward is introduced. It has two advantages: the unity signal transfer function and reduced signal swings inside the $\Sigma\Delta$ loop. These features greatly relax the DC gain and output swing requirements for Op-Amp in the low-voltage $\Sigma\Delta$ modulator. Implemented by a 0.18-${\mu}m$ CMOS technology, the $\Sigma\Delta$ modulator satisfies performance requirements for WCDMA and CDMA2000 standards.