A Low Noise Variable Gain Amplifier with 97.2 dB Linear Gain Range for CW Radar

This manuscript reports the design of a low noise variable gain amplifier (VGA) having wide dB linear gain characteristics for a continuous wave (CW) radar. A pseudo-exponential gain control function has been adopted in this VGA for the wide dB-linear behavior. Also, a BJT-based gain stage has been proposed to improve the gain dynamic range and low noise performance due to its higher transconductance/gain and lower flicker noise contribution. This proposed 2-gain stage VGA has been implemented in 130 nm SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. This design performance has been benchmarked by post-layout simulation results. It has demonstrated a voltage-controlled gain from-33.6 dB to 74.4 dB (total 108 dB), with a 97.2 dB linear gain range, input referred noise of 2.4 nV /root Hz, and power consumption of 4.25 mW. This VGA has a 3-dB bandwidth of 10 MHz at a maximum gain of 74.4 dB and 251 MHz at a minimum gain of-33.6 dB with a chip layout area of 0.0682 mm2. Compared to the latest available CMOS/BiCMOS VGAs in the literature, this proposed VGA has the highest gain dynamic range and dB-linear gain range with minimum input referred noise simultaneously across the operation bandwidth.