Fuente: Wipo "digitalization" According to an embodiment, an analog-to-digital converter includes a first AD (analog-to-digital) conversion circuit and a second AD conversion circuit. The first AD conversion circuit performs AD conversion of a first input signal to generate an upper-bit digital signal. The second AD conversion circuit performs AD conversion of a sampled signal to generate a lower-bit digital signal. The sampled signal is obtained by sampling a residual signal corresponding to a residue of the AD conversion in the first AD conversion circuit. A period during which the second AD conversion circuit performs AD conversion of the sampled signal overlaps a period during which a second input signal subsequent to the first input signal is settled.