Abstract
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 mu m SiGe BiCMOS technology. The measurement result shows the proposed VGA S (21) 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 Omega and the VGA performance is insensitive to temperature variation when measured from -40 to +80 A degrees C.