This paper describes the design of a baseband codec for European and North American digital cellular telephone applications. By integrating all the data conversion circuitry, this chip offers a low-cost, low-power solution to baseband signal processing and control functions. The receive section has two paths to process the in-phase and quadrature-phase components of the signal. Each path consists of a programmable gain amplifier (PGA) and a 10-b sigma—delta A/D converter. Two 8-b D/A converters generate the in-phase and quadrature-phase components of the transmit signal. A 9-b DAC and a 10-b DAC are provided to perform auxiliary control functions. The chip is fabricated using a 0.9-μm CMOS technology and has an area of 21 mm2. The average power dissipation is 85 mW.