An analog-to-digital converter includes a digital-to-analog converting circuit, a comparator, a comparator offset detector, and a signal processing circuit. The digital-to-analog converting circuit generates a reference voltage signal that changes in response to a comparator offset compensation signal, samples and holds an analog input signal, and performs a digital-to-analog conversion on digital output data to generate a hold voltage signal. The comparator compares the hold voltage signal with the reference voltage signal in response to a clock signal to generate a comparison output voltage signal. The comparator offset detector generates the comparator offset compensation signal based on the comparison output voltage signal. The signal processing circuit performs successive approximation based on the comparison output voltage signal to generate the digital output data.