Patent ID: 7205824

Claim:
An apparatus, comprising: a first transistor disposed in a substrate having a first, a second and a third terminal, the first terminal of the first transistor to be coupled to an external voltage and the second and third terminals of the first transistor to be coupled to a ground reference voltage; and a second transistor disposed in the substrate having a first, a second and a tap terminal, the first terminal of the second transistor coupled to the first terminal of the first transistor, the second terminal of the second transistor coupled to the second and third terminals of the first transistor and the tap terminal of the second transistor coupled to provide a tap voltage that is substantially proportional to a voltage between the first and second terminals of the second transistor up to a pinch-off voltage of the second transistor, and wherein the tap voltage is substantially constant and less than the voltage between the first and second terminals of second transistor when the voltage between the first and second terminals of second transistor is greater than the pinch-off voltage of the second transistor.