Patent ID: 8729966
Filing Date: 2014-05-20
Classification: H03G

Abstract:
1. A variable gain amplifier circuit for sending out, via an output terminal, a signal that is obtained by amplifying an input signal supplied via an input terminal, the variable gain amplifier circuit comprising: a plurality of amplification portions provided in parallel between an amplification coupling line and a grounding line each of the amplification portions including a switching device connected between the amplification coupling line and the grounding line and an amplification transistor including an input terminal that is connected to the input terminal, the amplification transistor inducing a current corresponding to the input signal to flow between the amplification coupling line and the grounding line according to the switching device when the switching device is in an on state, a gain of each of the amplification portions being varied by setting the switching device to the on state or an off state according to a gain control signal; and an output portion including an output transistor connected between the amplification coupling line and the output terminal, the output portion sending out a signal according to a bias voltage to the output terminal.