Patent ID: 8253492

Claim:
A variable gain amplifier, comprising: a plurality of direct current (DC) blocking capacitors configured to commonly receive an input signal at respective first terminals; a variable amplifier unit having a plurality of amplifier transistors configured to amplify outputs of respective second terminals of the plurality of DC blocking capacitors; a load impedance unit commonly coupled to a plurality of outputs of the variable amplifier; a plurality of bias resistors respectively having first terminals coupled to the respective second terminals of the plurality of DC blocking capacitors; a variable bias voltage generator having a plurality of bias voltage generator circuits each having a constant current source and a reference transistor coupled together in series, and each configured to apply a bias voltage to a second terminal of a corresponding one of the plurality of bias resistors; and a gain controller configured to control, independently of one another, a plurality of outputs of either the variable amplifier unit or the variable bias voltage generator.