Patent ID: 7633337

Claim:
A feedback-type variable gain amplifier, comprising: a first field effect transistor configured to receive an input voltage signal through an input node, to amplify the input voltage signal, and to output the amplified input voltage signal through an output node; a feedback circuit coupled between the input node and the output node, and configured to generate a feedback impedance that is changed in response to a control signal fed thereto; and a load circuit coupled between the output node and a voltage source, and configured to generate a load impedance that is changed in response to the control signal to cancel a change of an input impedance of the variable gain amplifier due to a change of the feedback impedance, wherein the load impedance and the feedback impedance are changed simultaneously in response to the control signal, and wherein the feedback circuit includes: a circuit of a capacitor, a resistor, and an inductor that are coupled in series between the input node and the output node; and a second field effect transistor coupled in parallel to the resistor between both ends of the resistor, and configured to operate in response to the control signal.