PDF folding for stochastic flash ADCs

A circuit is presented that halves the number of comparators required for a two-group stochastic flash ADC. In a two-group stochastic flash ADC, two Gaussian PDFs are shifted left and right by applying a global offset reference to the two groups of comparators. This creates a virtual uniform distribution of comparator offset between the two global offsets. Over half of the comparators fall outside of the virtual uniform distribution and are not used. The proposed circuit inverts the polarity of each comparator offset until it is within the useful range, creating a virtual uniform distribution of comparator offsets with few comparators wasted.