A flash analog-to-digital converter comprising a resistive reference ladder, a set of comparators for comparing the analog input signal with the reference voltages of the ladder to provide a digital code representing a coarse quantization of the input signal, a set of switches connected to the reference ladder and controlled by said digital code to provide an analog representation of the coarse quantization of the input signal, means to derive from said analog representation of the coarse quantization and from the input signal one or more residue signals and a fine analog-to-digital converter stage to generate a digital code representing a fine quantization of the one or more residue signals. For minimizing the number of switches required, each selector for one residue signal selects voltages of one half of the ladder at two values of the coarse quantization and the output signals of the two selectors for that residue signal are reversed by a crossover switch when the coarse quantization passes its center value.