Patent ID: 7400195

Claim:
A differential amplifier having a first input, a second input, a first output and a second output, comprising: a first differential circuit having a first input coupled to the first input of the differential amplifier, a second input, and first and second outputs respectively coupled to the first and second outputs of the differential amplifier; a second differential circuit having a first input coupled to the second input of the differential amplifier, a second input, and first and second outputs respectively coupled to the second and first outputs of the differential amplifier; a first impedance coupling the first output of the differential amplifier to the second input of the first differential circuit; a second impedance coupling the second output of the differential amplifier to the second input of the second differential circuit; a third impedance coupling the second input of the second differential circuit to the second input of the first differential circuit; and a common-mode detection and feedback control circuit coupled to the outputs of the differential amplifier for controlling the current source; wherein at least one of the first, second and third impedances is a variable impedance, wherein the first and second inputs of each of the first and second differential circuits correspond to the respective gates of a differential pair of transistors of the circuits, and wherein the differential circuits each comprise current sources for biasing their outputs.