Patent ID: 7795954

Claim:
A device for providing a substantially constant current, comprising: a first current mirror comprising a first transistor connected to a fixed voltage source through a first resistor, which provides a first bias current, and a second transistor connected to a variable voltage source, a drain current of the first transistor comprising a first amount of the first bias current; and a second current mirror comprising a third transistor connected to the variable voltage source through a second resistor, which provides a second bias current, and a fourth transistor connected to the fixed voltage source through the first resistor, a drain current of the fourth transistor comprising a second amount of the first bias current, wherein the second bias current increases in response to an increase in a variable voltage from the variable voltage source, and is mirrored into the fourth transistor by the third transistor through the second current mirror, increasing the second amount of the first bias current, and wherein the first amount of the first bias current decreases in response to the increased second amount of the first bias current, the decreased first amount of first bias current being mirrored into the second transistor by the first transistor through the first current mirror, the mirrored first amount of the first bias current compensating for a potential increase in a drain current of the second transistor caused by the increase in the variable voltage to provide the substantially constant current.