an analog to digital conversion circuit is disclosed including a fully differential reference voltage source . the reference voltage source includes a programmable current supply adapted to drive a programmed current through a resistor so as to establish an initial reference voltage . the initial reference voltage is sampled onto a capacitive network during a first sampling time interval . the capacitive network is coupled to a differential input of a fully differential amplifier , and maintained at a differential output of the differential amplifier during a second output time interval . an output coupling between the differential output and differential input of the differential amplifier acts to maintain stability of the output voltage during the output time interval .