Abstract
A novel variable gain amplifier for broadband application is proposed with a tapered traveling wave matching network, an output RC network and a cascode gain stage. The traveling wave matching network and RC network lessens input and output return loss dependence on VGA’s gain which is adjusted by biasing of the gain control circuit respectively. The proposed wide band (DC-12GHz) VGA is implemented in 2µm InGaP/GaAs HBT (fT of 29.5GHz) technology with die size of 1×2mm2. As gain control voltage sweeps, the VGA shows a gain tuned from −15dB to 15dB, while S11 (lower than −15dB) and S22 (lower than −10dB) almost unchanged over the operation frequency band.
