A 2.7 V CMOS GSM/WCDMA continuous-time filter with automatic tuning

Abstract

A 5th-order continuous-time baseband filter with 7-step gain control for a dual-mode cellular phone was implemented. A cascade of a real pole and a ladder filter implementing the complex pole pairs was used for low noise. The GBW of the opamps was made programmable to reduce the power consumption in the GSM-mode. The corner frequency tuning was facilitated by integrating a 1-bit DAC with the filter and a digital tuning circuit separately with an ADC. The integrated input referred noise is 6.9 /spl mu/V and 13.6 /spl mu/V and the circuit consumes 13 mW and 21.8 mW in the GSM- and WCDMA-modes, respectively. The IIP3 is +25 dBV in the WCDMA-mode.