Patent ID: 7545210

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 first gain setting network that includes a first impedance series coupled to a second impedance between the output terminal and a reference terminal, wherein a first common point between the first impedance and the second impedance is coupled to a first intermediate node, wherein a first gain associated with the first gain setting network is determined by the ratio of the first impedance and the second impedance; a second gain setting network that includes a third impedance series coupled to a fourth impedance between the output terminal and the reference terminal, wherein a second common point between the third impedance and the fourth impedance is coupled to a second intermediate node, wherein a second gain associated with the second gain setting network is determined by the ratio of the third impedance and the fourth impedance, and where the second gain is different from the first gain; a switching circuit that includes a first switching terminal coupled to the inverting input of the operational amplifier, a second switching terminal coupled to the first intermediate node, and a third switching terminal coupled to the second intermediate node, 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 in response to the user initiated gain setting, wherein gain 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 time averaged modulation between the first gain setting network and the second gain setting network such that a gain of the programmable gain amplifier is a blend of the gain settings.