Patent ID: 7545209

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 gain select circuit that is arranged as a first variable resistance circuit with a first resistance between the output terminal and a first intermediate terminal, a second resistance between the first intermediate terminal and the inverting input terminal, and a third resistance between the inverting input terminal and the reference terminal, wherein values associated with the second resistance and the third resistance are varied in response to a gain select control signal; a gain adjust circuit that is arranged as a second variable resistance circuit with a fourth resistance between the output terminal and a second intermediate terminal, and a fifth resistance between the second intermediate terminal and the reference terminal, wherein values associated with the fourth resistance and the fifth resistance are varied in response to a gain trim setting control signal, wherein the first intermediate terminal is coupled to the second intermediate terminal; and a control circuit that is arranged to provide the gain select control signal and the gain trim setting control signal in response to the user initiated gain setting.