a circuit for supplying regulated first and second supply voltages to the amplifier / comparator of a recirculation of remainder analog to digital converter , comprises a series pair of transistors connected as emitter followers between unregulated voltage sources . outputs of the emitter followers carry the regulated supply voltages and are applied to the supply terminals of the amplifier / comparator . a pair of diodes connected in series between the bases of the emitter followers establish the magnitudes of the two regulated supply voltages . the junction voltage between the two zener diodes is controlled by a difference amplifier that in turn is responsive to an analog input voltage and the output of the amplifier / comparator . the output of the difference amplifier causes the regulated supply voltages to track a common mode signal component inherent in the converter and thereby improves component accuracy . another pair of zener diodes between the output of the amplifier / comparator and the input to the difference amplifier prevents saturation of the amplifier / comparator by reducing the magnitude of the regulated supply voltages when the amplifier / comparator is in a comparator mode .