A wideband variable gain amplifier with feedback DC-offset correction in 0.13µm CMOS technology

A low power and area optimized wideband variable gain amplifier (VGA) has been designed in 0.13 μm CMOS technology for an integrated Synthetic Aperture Radar (SAR) receiver. The VGA consists of three gain stages. The first stage is a resistively loaded, fixed gain source coupled pair, while the other two are variable gain degenerated differential pairs. Each stage also utilizes negative Miller capacitance to extend the bandwidth, resulting in a VGA configuration with -3 dB bandwidth of 1 GHz. The gain of the VGA can be continuously varied from 10 dB to 30 dB. The input-referred noise density is 2.8 nV/√Hz and the out-of-band IIP3 is -1 dBm. The circuit consumes only 5.25 mW from a 1.2 V supply (excluding the output buffer) and occupies 0.037 mm² die area.