Abstract
This thesis implements a complementary metal oxide semiconductor (CMOS) linear-in-dB VGA with digitally controlled gain. This VGA adopts the degeneration- type current amplifier to vary current gain. A voltage-to-current converter and a current-to-voltage converter are added for measurement convenience. And a digital-based DC offset calibration loop is proposed to achieve the DC offset cancellation. An experimental chip is fabricated in TSMC 0.18 µm CMOS process and its total area 1023 × 1023 μm2. The VGA provide 51 dB gain range with 5.1 dB step and more than 10 MHz bandwidth. The current consumption from a single 1.8 V supply is less than 11.45 mA. The total harmonic distortion (THD) is small than -46.75 dB at the minimum gain setting when input signal is 1-MHz sinusoidal waveform with 400mVppd swing. The input referred noise is 3.36 at maximum gain setting. The output DC offset after calibration is less than the 30mV when 30 mV input DC offset is applied.