Patent ID: 11616475

Abstract:
Circuits and methods for improving the noise figure (NF) of an amplifier, particularly an LNA, in high-gain modes while improving the IIP3 of the amplifier in low-gain modes. The source of an amplifier common-source FET is coupled to circuit ground thorough a degeneration circuit comprising a two-port inductor and a bypass switch coupled in parallel with the inductor. A switched feedback circuit is coupled between the gate of the common-source FET and a feedback node in the amplifier output signal path. During a low gain mode, the inductor is entirely bypassed and the enabled feedback circuit lowers the input impedance of the common-source FET and reduces the gain of the amplifier circuit, essentially eliminating the need for a degeneration inductor. During a high gain mode, the source of the common-source FET is coupled to circuit ground through the inductor and the feedback circuit is disabled. Other gain modes are supported.