Patent ID: 8730080

Claim:
An analog-to-digital converter comprising: a sampling-voltage providing circuit providing a group of first comparison voltages and a group of second comparison voltages; a first comparison circuit, coupled to the sampling-voltage providing circuit, for performing a first comparison operation to an analog-signal input quantity according to the group of first comparison voltages to generate a first comparison digital quantity; a second comparison circuit, coupled to the sampling-voltage providing circuit and the first comparison circuit, for selecting second comparison voltages among the group of second comparison voltages according to the first comparison digital quantity and performing a second comparison operation to the analog-signal input quantity according to the selected second comparison voltages to generate a second comparison digital quantity; and an encoder circuit, coupled to the first comparison circuit and the second comparison circuit, for encoding the first comparison digital quantity and the second comparison digital quantity and generating a digital quantity corresponding to the analog-signal input quantity, wherein the second comparison circuit comprises: a decoder circuit, coupled to the first comparison circuit, for performing a decoding operation to the first comparison digital quantity to obtain a selection-signal digital quantity.