Patent ID: 6020730
Filing Date: 2000-02-01
Classification: G05F

Abstract:
A current source comprising:a current source FET having a source, a gate, and a drain, said current source FET having a drain-to-source bias voltage applied between the drain and the source, said gate having a substantially constant gate bias voltage applied thereto, thereby causing the current source FET to have a substantially constant current flow from drain to source when the drain-to-source bias voltage on the current source FET is sufficiently high to cause the current source FET to operate in a region of saturation;a control FET having a source coupled to the drain of the current source FET, and a gate having a control voltage applied thereto, wherein when said control voltage, when dropped, reduces the drain-to-source bias voltage on the current source FET, thereby stopping the current source FET from operating in a region of saturation and reducing the current flow in the current source FET;a driver circuit for generating the control voltage, the driver circuit including a switch coupled between the gate of the control FET and the source of the current source FET; anda resistor coupled between the gate of the control FET and a first supply voltage, wherein the first supply voltage is great enough so that when applied to the gate of the control FET, the current source FET operates in the region of saturation.