Design of CMOS Variable Gain Amplifier for DTV Tuners

A CMOS variable gain amplifier (VGA) is designed, which is suitable for the turner of digital video broadcasting-cable(DVB-C). The amplifier is consists of exponential control circuit, amplifier circuit and common mode feedback circuit. The exponential circuit is presented by an approximate exponential function. The VGA is fabricated in 0.35 mum CMOS technology, and is simulated by Mentorpsilas circuit simulation tool Eldo. Simulation results show that the VGA core consumes 4.63 mW at 3.3 V supply voltage and has a gain range from 0 to 32 dB. The frequency range is 46 MHz~267 MHz and noise figure is less than 10 dB.