Analogue to digital converter

Abstract

An analogue to digital converter (ADC) of the recirculating type is described. In one embodiment, the ADC is composed of three storage and residual determination units, which, in cooperation with an operational amplifier, and suitable comparator means, are operable to re-present residual signals for analogue to digital conversion. To enhance settling at the beginning of a cycle, the first storage and residual determination unit is used once, with remaining recirculation being conducted between the other two storage and residual determination units. Another embodiment presents a recirculating ADC stage which comprises a plurality of capacitor banks operable to be switched into and out of connection with other components of the ADC stage, in order to recirculate residual values for calculation of further bits of a digital output. Each bank comprises a plurality of capacitors, and cooperating switching means for connecting each bank in turn with the other components. The switching means are controlled by timing signals, wherein the switching means for each capacitor in each capacitor bank interpose the same number of switches between that capacitor and fed-back signals to that capacitor as to other capacitors of that bank.