A converter comprises an input terminal to receive a first analog signal, a digital-to-analog converter to provide second analog signals related to digital values applied to the digital-to-analog converter. A comparator is coupled to receive the first and second analog signals, the comparator also comprising a variable-gain amplifier to provide an output signal based on a difference between the first and second analog signals. A state machine receives the output signal of the comparator and to generate the digital values applied to the digital-to-analog converter based on the output signal of the comparator and a controller sets the gain of the variable-gain amplifier selectively.