Low-Noise, Gain-Selectable Amplifier

Traditional gain-selectable amplifiers use switches in the feedback loop to connect resistors to an amplifier, but the switch resistance degrades the noise performance of the amplifier, adds significant capacitance on the inverting input, and contributes to nonlinear gain error. This article presents a gain-selectable amp that uses an innovative switching technique that preserves the noise performance while reducing the nonlinear gain error.