Patent ID: 7605659

Claim:
A programmable gain amplifier circuit for receiving an input signal and providing an output signal with an adjustable gain corresponding to a user initiated gain setting, the programmable gain amplifier circuit comprising: an operation amplifier circuit including a non-inverting input terminal configured to receive the input signal, an inverting input terminal configured to receive a feedback signal, and an output terminal configured to provide the output signal; a digitally controlled potentiometer that is coupled between the output terminal and a reference terminal, wherein the digitally controlled potentiometer includes a wiper terminal that is coupled to the inverting input terminal, wherein the digitally controlled potentiometer has a first resistance value between the output terminal and an intermediate node, a second resistance value between the intermediate node and the wiper terminal, and a third resistance value between the wiper terminal and the reference terminal, wherein the second and third resistance values vary in response to a gain select control signal by adjusting a wiper setting for the digitally controlled potentiometer; a first capacitor circuit that is coupled between the reference terminal and the intermediate node; a second capacitor circuit that is coupled between the output terminal and the intermediate node; a resistor circuit; a switching circuit that includes a first switching terminal coupled to the intermediate node through the resistor circuit, a second switching terminal coupled to the reference terminal, and a third switching terminal coupled to the output terminal, wherein the switching circuit is arranged to couple the first switching terminal to the reference terminal in a first position, wherein the switching circuit is arranged to coupled to the first switching terminal to the output terminal in a second position, and wherein the switching circuit selects one of the first position and the second position in response to a gain trim control signal; and a control circuit that is arranged to provide the gain control signal and the gain trim control signal in response to the user initiated gain setting, wherein the gain trim control signal is modulated such that the switching circuit oscillates between the first position and the second position according to a duty cycle assigned to the user initiated gain setting, wherein the duty cycle corresponds to the time averaged modulation between the first position and the second position.