A Compact 3.5–11-GHz VGA With 32-dB Gain Tuning Range in 130-nm SiGe BiCMOS

This letter presents a compact ultrawideband variable gain amplifier (VGA) with large gain tuning range and low phase error implemented in 130-nm SiGe BiCMOS process. First, the series RLC-based feedback technique (SRFT) is used to efficiently expand the bandwidth, which is combined with inductorless passive switching attenuators to realize large gain tuning range with less inductors. Next, the phase compensation inductor is introduced between stages to decrease phase variation under different gain states. This design achieves 32-dB gain tuning range with 1-dB gain step in the operation band of 3.5–11 GHz, and the core area is only 0.47 mm². The gain flatness is less than 1 dB, and the maximum rms phase error is 3.9° in the operation band.