Patent ID: 8319550

Claim:
A method of operating a programmable-gain amplifier which has a plurality of capacitors, an attenuation capacitor, and a differential amplifier, wherein a first terminal of each of the plurality of capacitors is coupled to a minus input of the differential amplifier, the method comprising: receiving a gain select signal which indicates a selected subset of capacitors of the plurality of capacitors and an unselected subset of capacitors of the plurality of capacitors, wherein the selected subset includes at least one capacitor of the plurality of capacitors, and wherein the selected subset and the unselected subset are mutually exclusive; during a sampling phase of the programmable-gain amplifier: coupling a first input signal to a second terminal of each of the plurality of capacitors, wherein each of the plurality of capacitors are coupled in parallel with each other; during a gain phase of the programmable-gain amplifier: coupling the second terminal of each capacitor of the selected subset of capacitors indicated by the gain select signal to a plus output of the differential amplifier; and when the unselected subset of capacitors includes at least one capacitor, coupling the second terminal of each capacitor of the unselected subset of capacitors to a first power supply terminal, wherein a gain of the programmable-gain amplifier is based on a ratio between a capacitance of the selected subset of capacitors and a capacitance of the unselected subset of capacitors; and during the gain phase of the programmable-gain amplifier: coupling a first terminal of the attenuation capacitor to the minus input of the differential amplifier and coupling a second terminal of the attenuation capacitor to the plus output of the differential amplifier, wherein the gain of the programmable-gain amplifier is attenuated based on a capacitance of the attenuation capacitor.