High frequency/high dynamic range CMOS VGA and mixer with a novel variable gain method

Abstract

A novel CMOS Variable Gain Amplifier (VGA) having high frequency and high dynamic range combined with a mixer is proposed. In order to have variable gain, it uses the principle of "Transconductance of a MOS device varies with Vds" and to increase bandwidth, it also uses cascode structure. So its main structure is very similar to a conventional cascode amplifier. This VGA has a controllable gain range of -45dB to +45dB by external control voltage as well as enhanced operating frequency range over than 200MHz. It is fabricated in 0.35μm CMOS technology with the core area of 580μm x 660μm. It consumes only 10.8mA at 3.3V supply voltage. Also new mixer has been proposed to increase bandwidth of VGA. It has a cascode structure with the VGA. Since this scheme can reduce the output loading effect of VGA, we can easily extend its operating range more than 400MHz.