A 120dB all CMOS variable gain amplifier based on new exponential equation

This paper presents the design of a two-stage wide dynamic range variable gain amplifier (VGA). This is based on a new approximated exponential equation which offers a wide decibel linear range and an improved fully differential MOS Cherry-Hooper topology. In addition, the bandwidth of the VGA has been extended by using the capacitive neutralization technique for wide-band applications. Simulation results based on a 0.13-μm CMOS technology demonstrate that the gain variation range of the VGA is 120dB (from -79 ~ 41 dB) when control voltage changes from -0.8V to 0.8V. The -3dB bandwidth of the VGA at the maximum gain is 132MHz and the overall current consumption is 3.34mA if the V dd =1.2V and the V ss =-1.2V.