Abstract: A ramp generator circuit includes: a reference signal generator circuit which generates a ramp waveform having a slope obtained by multiplication using a power of 2 according to a value of a higher order bit of a gain control signal; a clock control circuit which selectively outputs 2^m kinds of fractional-N clocks according to one of 2^m (natural number) areas obtained by dividing a code range represented by a lower order bit, when a negative gain is set; and a variable gain circuit which sets a ramp waveform according to the value of the gain control signal, and sets a ramp signal amplitude in each area so that a period ratio between ramp driving clocks for adjacent areas and a ratio between an amplitude of a ramp signal when the standard gain is set and a largest amplitude of a ramp signal are equal.