Patent ID: 8786359
Filing Date: 2014-07-22
Classification: G05F

Abstract:
1. A circuit comprising: a current mirror including a first set of transistors and a second set of transistors, at least one of the transistors in the first set of transistors and at least one of the transistors in the second set of transistors in a cascode arrangement; a first operational amplifier coupled to the first set of transistors and including an input of a first bias voltage determined by a reference voltage circuit; a second operational amplifier coupled to the second set of transistors and including an input of a second bias voltage determined by the reference voltage circuit that sets the second bias voltage to one of a plurality of selectable voltage levels within a range of voltages; wherein a first transistor of the first set of transistors has an input coupled to a voltage supply and an output coupled to an input of a first transistor of the second set of transistors, wherein an output of the first transistor in the second set of transistors is provided as an input to the first operational amplifier to define a first feedback loop, wherein the output of the first transistor in the first set of transistors is provided to an input of the first transistor of the second set of transistors, wherein a second transistor of the first set of transistors has an input coupled to the voltage supply and an output coupled to an input of a second transistor of the second set of transistors, wherein the second transistor of the second set of transistors has an output that drives an output current to a different voltage domain, wherein the different voltage domain has a voltage supply limited by the second bias voltage, and wherein the second transistor of the second set of transistors is directly coupled to the second operational amplifier; and a current source coupled to the first transistor of the second set of transistors; wherein the current source is an active device that includes cascode transistors; and wherein each transistor of the second set of transistors is controlled by the second operational amplifier.