Variable gain circuit and radio apparatus using the same

摘要

A gain switching circuit comprises first and second gain stages connected in parallel between the input terminal and the output terminal, and a control unit for allowing the first and second gain stages to be selectively operative, wherein the first and second gain stages respectively include input sections in which input impedance values viewed from the input terminal are substantially equal to each other, and output sections in which output impedance values viewed from the output terminal are substantially equal to each other. By this configuration, a gain switching circuit and a radio apparatus using such a gain switching circuit adapted so that input/output impedance does not fluctuate are provided without implementing switching between gain stages.