Patent ID: 7855576

Claim:
A circuit comprising: voltage generator circuitry operable to generate a plurality of voltage signals of substantially different voltages; multiplexer circuitry with voltage inputs coupled to said voltage signals, wherein said multiplexer circuitry is operable to select a reference signal from among said voltage inputs; operational amplifier (“op-amp”) circuitry with a first input coupled to said reference signal and a second input coupled to an output signal of said op-amp circuitry, wherein said op-amp circuitry is coupled to function as a voltage follower, and wherein said multiplexer circuitry selects said reference signal independently of said op-amp circuitry; switching circuitry coupled to a third input of said op-amp circuitry, wherein said switching circuitry is coupled to a source of relatively high voltage; and resistor circuitry coupled to said third input and a source of relatively low voltage.