US Patent 7557657 Variable gain amplifier with wide gain variation and wide bandwidth

A variable gain amplifier including: a differential amplification unit amplifying and outputting a difference between a first input signal and a second input signal inputted via a first input terminal and a second input terminal, respectively, according to a first bias current of the first input terminal and second input terminal, to a first output terminal and a second output terminal; a diode-connected load unit comprising loads diode-connected to the first output terminal and second output terminal, respectively, the load receiving a second bias current; and a gain control unit controlling a gain between the input terminals and the output terminals of the differential amplification unit by controlling the size of the first bias current and second bias current.