A low power SiGe BiCMOS baseband circuitry for a direct conversion CMMB tuner IC

An analog baseband circuitry for a China Mobile Multimedia Broadcasting (CMMB) direct conversion tuner IC is introduced in this paper. It includes an 8^th order channel select filter with sharp transition band and utilizes a novel gain-bandwidth-product (GBW) extension technique in designing the low power, high speed operational amplifiers (Op-Amps) of the active-RC filter. A current steering type variable gain amplifier (VGA) is adopted to provide more than 40 dB baseband gain range and an on-chip DC offset cancellation (DCOC) circuit is designed to prevent the baseband chain from saturation due to DC offsets. The chip is fabricated in a 0.35-μm SiGe BiCMOS process and consumes 15mA from 3V supply with filter´s f_-3dB at 4 MHz.