A wideband BiCMOS variable gain amplifier with novel continuous dB-linear gain control and temperature compensation

In this paper, we present an accurate analog decibel linear control circuit for variable gain amplifiers (VGAs). The proposed circuit features simple and effective dB-linear control for current steering VGAs. A novel temperature compensation circuit is also proposed for this VGA. Based on the proposed circuit design techniques, a wideband single stage VGA with accurate analog dB-linear gain control and temperature compensation is realized in Tower Jazz 0.18 μm SiGe BiCMOS technology. The measurement result shows the proposed VGA S21 gain is tunable from −50 to +20 dB with a −3 dB bandwidth of about 4.6 GHz. The measured IIP3 is from −29 to −8 dBm for maximum and minimum gain respectively and dissipates about 11 mA current from a single 1.8 V supply. The measured noise figure at maximum gain is about 8.5 dB when matched to 50 Ω and the VGA performance is insensitive to temperature variation when measured from −40 to +80 °C.