Patent ID: 7276962
Filing Date: 2007-10-02
Classification: H03F,H03G

Abstract:
1. A switched capacitor programmable gain amplifier (PGA) that is arranged to provide an output signal that is gain scaled from an input signal, the switched capacitor PGA comprising: a differential amplifier circuit that includes a first input terminal, a second input terminal, and an output terminal; a first capacitor circuit that is coupled between the input signal and the first input terminal, and arranged to provide a nominal capacitance for an adjustable sampling capacitor circuit; a second capacitor circuit that is coupled between a first intermediate node and the first input terminal, and arranged to provide an offset capacitance for the adjustable sampling capacitor circuit; a constant VGS switching circuit that is arranged to selectively couple the first intermediate node to the input signal in response to a gain control signal such that the effective capacitance is determined by the nominal capacitance and the offset capacitance; a first switching circuit that is arranged to selectively couple the first intermediate node to a predetermined voltage in response to an inverse of the gain control signal; a second switching circuit that is arranged to selectively couple the first input terminal to a predetermined voltage during a sampling phase of the switched capacitor PGA; a third switching circuit that is arranged to selectively configure the adjustable sampling capacitor circuit for an amplification phase of the switched capacitor PGA; a feedback capacitor circuit that is coupled between the first input terminal and a feedback intermediate node; a fourth switching circuit that is arranged to selectively couple the feedback intermediate node to the predetermined voltage during the sampling phase of the switched capacitor PGA; and a fifth switching circuit that is arranged to selectively couple the feedback intermediate node to the output terminal of the differential amplifier circuit during the amplification phase of the switched capacitor PGA.