A CMOS Low-Distortion Variable Gain Amplifier with Exponential Gain Control

In this paper, a CMOS low-distortion variable gain amplifier with exponential gain control is developed by utilizing a transconductance linearization scheme. The VGA is composed of a VGA core based on current-steering structure, an exponential voltage generator based on transfer characteristics of differential pair, and a stage of fixed gain amplifier. The proposed VGA circuit was verified in 0.25 mum CMOS technology, the measurement results show a total gain control range of 40 dB, the 3-dB bandwidth is 100 MHz, and a -58.5dBc third-order inter-modulation distortion at differential output of 2 Vpp are obtained, the noise figure at maximum gain is 8.6 dB.