Cmos variable gain amplifier

A CMOS variable gain amplifier comprising:

• a cascode amplifier comprising:
• an input stage comprising a pair of common source field effect transistors into which differential input voltage signals are differentially inputted in a triode region;
• and
• a cascode stage comprising a pair of common gate field effect transistors of which sources are cascode-coupled to drains of the pair of common source field effect transistors, respectively,
• wherein the cascode amplifier varies transconductance of the input stage in accordance with a gain control voltage signal applied as a common gate voltage of the cascode stage;
• a first current generation unit connected in parallel to a drain of the cascode stage and configured to vary a flowing current in accordance with the gain control voltage signal and control a current flowing into the cascode stage to vary transconductance of the cascode stage;
• a second current generation unit connected to a common source of the input stage and configured to vary a flowing current in accordance with the gain control voltage signal and control a bias current flowing in the cascode amplifier;
• a current control unit configured to generate a current control signal for the first and second current generation units in accordance with the gain control voltage signal;
• and
• a load stage connected in series to the drain of the cascode stage and configured to output an output current, which is varied by the overall transconductance of the cascode amplifier, as a differential output voltage.