Patent ID: 7119611

Claim:
An integrated circuit amplifier, comprising: an internal amplifier having a first output coupled to a non-inverting input through an interface; said internal amplifier having a second output for providing an output signal of the integrated circuit with an associated output impedance; a series resistance element coupled between said first and second outputs; said internal amplifier including a first stage of amplification to provide current drive at said first output and through said interface, and a second stage of amplification to provide current drive at said second output through said series resistance element and said interface; said second stage of amplification comprising a transresistance device for driving said second output; said output impedance being a function of a ratio of a current drive of the first and second outputs and the value of said series resistance element; a voltage on said second output being a function of said interface and a current input to said internal amplifier; and wherein said transresistance device is comprised of a plurality of parallel transistors, each being selectable to allow for any combination of said parallel transistors to be combined to form said transresistance device, said configuration of said parallel transistors determined by an external calibration signal.