Wideband 28-nm CMOS Variable-Gain Amplifier

This paper discusses a wideband variable-gain amplifier (VGA) implemented in a 28-nm FDSOI CMOS technology. This VGA employs optimal-biasing and differential largesignal pre-distortion linearizations that operate over all gain settings and over its frequency range. The 0.4-to-4-GHz VGA, which consists of its core circuit and an output buffer, exhibits a wideband gain ranging from 4.6 to 12 dB in 1-dB steps and an input return loss higher than 10 dB while demonstrating a worst-case IM3 of -54 dBm across the gain range at ~0-dBm output power and noise figures from 3 to 5.9dB at 12 dB gain. The VGA and buffer consume 15mA and 60mA from a 1.5V supply, respectively. The total chip area, including the bond pads, is 1 × 1mm².