1. A circuit for converting an analog voltage to a digital signal comprising: a plurality of voltage comparators including a highest-order comparator and a lowest-order comparator, each of said comparators having at least first and second inputs and an output; a corresponding voltage source for each of said comparators having an output connected to the first input of said voltage comparators and wherein the voltage sources other than the highest-order voltage source have at least one input control point; an analog input sampling unit having an output connected to the second input of each of said voltage comparators; a register having a plurality of inputs and outputs, each of said register inputs connected to an output of a corresponding comparator; and wherein each one of the outputs from the register defines an output for the circuit and at least one of a higher-order portion of the outputs from said register exclusively feeds forward to at least one of the input control points of a voltage source for a lower-order comparator to help determine a voltage reference level for the lower-order comparator.