Patent ID: 8102209

Claim:
A complementary metal-oxide semiconductor (CMOS) variable gain amplifier comprising: a cascode amplifier comprising a common source field effect transistor and a common gate field effect transistor which are connected in a cascode structure; a first current generation unit connected in parallel to a drain of the common gate field effect transistor and configured to vary transconductance of the cascode amplifier in accordance with a gain control voltage signal applied to a gate of the common gate field effect transistor of the cascode amplifier; a second current generation unit connected to a common source of the cascode amplifier and configured to control a bias current of the cascode amplifier in accordance with the gain control voltage signal; 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 a drain of the cascode amplifier and configured to output an output current, which is varied by the overall transconductance of the cascode amplifier, as a differential output voltage.