A low-power switched-capacitor variable gain amplifier

A novel power reduction technique is proposed for a switched-capacitor amplifier (SCA) with two-stage operational amplifier. This technique improves both the bandwidth and the slew rate of the SCA with only two additional switches, and therefore, the power consumption of the SCA is reduced. This power reduction technique is applied to a variable gain amplifier (VGA) which is implemented in an analog front-end of camera modules for cellular phones. This reduces 30% of the VGA power consumption compared to the conventional one. Fabricated in 0.25-mum CMOS process with 3.3-V transistors and MIM capacitors, the VGA occupies 0.49 x 0.49 mm(2) and dissipates 18.7 mW at 18 MHz with a supply voltage of 3.1 V.