Patent ID: 7528658

Claim:
An apparatus, comprising: a first stage amplifier having an input and an output, the first stage amplifier is a differential amplifier, wherein the input of the first stage amplifier comprises first and second inputs and the output of the first stage amplifier comprises first and second outputs; a second stage amplifier having an input and an output, the input of the second stage amplifier is operably coupled to the output of the first stage amplifier, the second stage amplifier is a differential amplifier, wherein the input of the second stage amplifier comprises first and second inputs and the output of the second stage amplifier comprises first and second outputs, wherein the first input of the second stage amplifier is coupled to the first output of the first stage amplifier and the second input of the second stage is coupled to the second output; a first bias circuit operable to set a common mode voltage of the first amplifier; a second bias circuit operable to set a common mode voltage of the second amplifier; a first feedback circuit operably coupled to the first bias circuit and the output of the first stage, the first feedback circuit is operable to control the common mode voltage of the first stage amplifier based on the common mode voltage set by the first bias circuit and the output of the first stage amplifier; and a second feedback circuit coupled to the second bias circuit and the output of the second stage, the second feedback circuit is operable to control the common mode voltage of the second stage amplifier based on the common mode voltage set by the second bias circuit and the output of the second stage amplifier.