Patent ID: 6566958
Filing Date: 2003-05-20
Classification: H03F

Abstract:
An apparatus for biasing current at a rail-to-rail stage of an amplifier, the apparatus comprising:a first transistor having a base and a collector, a second transistor having a base and a collector, the collector of the second transistor being coupled to the collector of the first transistor; a third transistor having a base and a collector, the third transistor coupled in emitter follower arrangement with the first transistor, a fourth transistor having a base and a collector, the fourth transistor coupled in emitter follower arrangement with the second transistor; a fifth transistor having a base and a collector, wherein the base of the fifth transistor is coupled to the base of the first transistor, a sixth transistor having a base, an emitter, and a collector, wherein the base of the sixth transistor is coupled to the base of the second transistor, wherein the emitter of the sixth transistor is coupled to the collector of the fifth transistor; a bias reference source coupled to the base of the third transistor at a first node and coupled to the base of the fourth transistor at a second node, the bias reference source operable to provide a bias reference signal; the first node operable to receive a first bias feedback signal; and the second node operable to receive a second bias feedback signal.