A variable-gain amplifier design based on g_m/I_D method

A variable gain amplifier(VGA) was designed based on Gm/ID method.The circuit was fabricated by SMIC 90nm CMOS technology model.It consists of a fixed-gain stage,two variable-gain stages and a gain controller.The fixed gain stage gives pre-amplification in order to boost the VGA's maximum gain.The VGA's gain tenability is provided by the two variable gain stages which controlled by the gain controller.The design synthesis is simplified and optimized using gm/ID method which enables us to characterize transistors in any operating region based on their gm/ID and VGS relation,and help us to design the low-voltage low-power circuit.In order to get wider gain rage,the proposed VGA utilizes a novel pseudo-power exponential function.The Spectre simulation results show that under 1.2V supply voltage the proposed VGA has 76 dB gain-range over 0.8 V control voltage range,with 34~183.6 MHz bandwidth,and 0.82 mW power consumption.