VARIABLE GAIN AMPLIFIER CIRCUIT AND WIRELESS COMMUNICATION APPARATUS

摘要

PROBLEM TO BE SOLVED: To suppress deterioration in high frequency characteristics caused by the change of current density and to suppress a change in input/output impedance at a gain variable time.

SOLUTION: A variable gain amplifier circuit comprises: a signal input terminal (RFin); a plurality of amplification transistors (Q1-Qn) connected in parallel between a power supply node (VCC) receiving a power supply voltage and a ground node (GND) receiving a ground voltage; a signal output terminal (RFout) connected between the plurality of amplification transistors (Q1-Qn) and the power supply node (VCC); a first switch circuit (SW1) for switching a connection destination of control terminals of the plurality of amplification transistors (Q1-Qn) individually to the signal input terminal (RFin) or to the ground node (GND) in response to a gain control signal from the outside; and a bias supply circuit for supplying bias voltages of the plurality of amplification transistors (Q1-Qn) to a first node between the first switch circuit (SW1) and the signal input terminal (RFin).

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