Abstract: This paper presents a novel approach for designing a reconfigurable variable gain amplifier (VGA) for the multi-mode multi-band receiver system RF front-end applications. The configuration, which is comprised of gain circuits, control circuit, DC offset cancellation circuit and mode switch circuit is proposed to save die area and power consumption with the function of multi-mode and multi-band through reusing. The VGA is realized in 0.18 μm CMOS technology with 1.8 V power supply voltage providing a gain tuning range from 5 to 87 dB when the control voltage varies from 0 to 1.8 V. The 3 dB bandwidth is about 80 MHz for all levels of control voltage (all gains). Also, the DC offset cancellation circuit can effectively suppress DC offset to a value of less than 40 mV at the output regardless of the input. The overall power consumption is less than 3 mA, and die area is 705 × 100 μm².

Key words: variable gain amplifier