A low gain error two-stage dB-linear variable gain amplifier in 0.35μm CMOS process

摘要

A CMOS linear-in-dB variable gain amplifier (VGA) is presented in this paper and the dB-linear gain is controlled linearly by the control voltage. The VGA incorporates a pre-amp, a gain control stage and a fixed gain amplifier. In order to ensure gain range and reduce gain error, a two-stage gain control stage is proposed. The proposed dB-linear VGA designed in a 0.35um CMOS process achieves a variable gain range of 50 dB with a ±0.7-dB gain error. For output voltage swing of 1Vp-p, the total harmonic distortion (THD) is -59dB while the control voltage is zero. The VGA can provide 75MHz 3dB bandwidth and the power consumption of the whole circuit is about 9.55mW with a ±2.5V power supply.