Variable gain amplifier

Abstract

In order to provide a high sensitivity variable gain amplifier, there is provided a structure in which at least one path comprising at least a stage of the voltage-input/voltage-output amplifier+a stage of voltage-input/current-output amplifier and a path comprising a stage of the voltage-input/current-output amplifier are connected in parallel between the input terminal and output terminal or, a structure in which a plurality of paths each comprising at least a stage of voltage-input/voltage-output amplifier+a stage of voltage-input/current-output amplifier are connected in parallel between the input terminal and output terminal. A gain is switched by selecting and operating any one of paths. When any one path is selected, an input impedance viewed from the input terminal is suppressed almost not to change or an output impedance viewed from the output terminal is suppressed almost not to change. Thereby, a high sensitivity wireless receiver can be realized.

Dependencies are inferred from the claim text.