Variable gain amplifier and a communication device provided with the variable gain amplifier

摘要

PROBLEM TO BE SOLVED: To provide a variable gain amplifier capable of obtaining a wide variable gain range and suppressing the degradation of linearity when switching an amplification stage transistor.;SOLUTION: The variable gain amplifier 1 comprises the amplification stage transistor Q connected to a signal input end IN and a plurality of cascode stage transistors T cascode-connected to the output end of the amplification stage transistor Q and is further provided with a plurality of cascode amplifiers Amps connected in parallel through an attenuator AT. Further, the variable gain amplifier 1 comprises a gate potential control circuit 20 for controlling on/off-operations of the plurality of cascode stage transistors included in the respective cascode amplifiers Amps, and a base current control part 11 for controlling on/off-operations of the plurality of amplification stage transistors Q so as to turn on only one selected amplification stage transistor Q.;COPYRIGHT: (C)2008,JPO&INPIT