Patent ID: 7132880

Claim:
A circuit comprising: an operational amplifier; a source follower transistor coupled to a power supply to provide a voltage at its source terminal, in which the source terminal has a low output impedance, the source follower transistor also having filtering to reduce noise from the power supply; a first transistor having a gate terminal coupled to an output of the operational amplifier and also having a first terminal coupled to the source terminal of the source follower transistor and a second terminal coupled to an output node to provide an output voltage to which a load is to be coupled, in which the load is operable to draw a first current from the output node during operation; and a second transistor coupled to the first transistor to draw a second current from the output node which is inversely proportional to the first current drawn by the load during operation to maintain a substantially constant current through the first transistor to regulate the output voltage, wherein a gate terminal of the second transistor is coupled to the output of the operational amplifier and wherein the second transistor has a third terminal coupled to the output node and a fourth terminal coupled to a supply return.