A low-power-consumption linear-in-dB CMOS VGA

This paper presents a low-power and small-size variable gain amplifier (VGA) which consumes only 1.1mW and occupies only 132um × 59um in 0.18-um CMOS technology. The proposed circuit is implemented by Gilbert cells and an exponential function circuit for the dB linearity of the gain voltage. The gain of the VGA can be varied linearly in dB from -10dB to 50dB with respect to a control voltage from 0.2V to 0.85V. The operation frequency is only 10MHz, but the VGA maintains 3dB-bandwidth wider than 46MHz throughout its gain range. At the worst case, the amplitude of the output can be 300mV when THD is lower than -40dBc. The total simulation is based on TSMC 0.18um. Low power consumption is obtained owing to high transition frequency of the transistors in 0.18-um CMOS technology.