Photoelectric conversion device, imaging system, and mobile apparatus

A photoelectric conversion device comprising:

• a pixel configured to generate a first signal in accordance with an incident light by photoelectric conversion;
• an amplifier unit configured to amplify the first signal to output a second signal;
• and
• a comparator unit configured to compare a voltage of the second signal with a voltage of a reference signal,
• wherein in a first period that is a period before the voltage of the second signal is settled, the voltage of the reference signal is a reference voltage,
• wherein in the first period, the comparator unit compares the voltage of the second signal with the reference voltage to generate a determination result signal used for setting a gain,
• wherein in a second period that is a period after the voltage of the second signal is settled, the reference signal has a ramp waveform whose voltage changes in accordance with time,
• wherein in the second period, the comparator unit compares the voltage of the second signal with a voltage of the ramp waveform to perform analog-to-digital conversion,
• wherein a slope of the ramp waveform is configured to be switched between a first slope α and a second slope β,
• wherein the reference voltage is configured to be switched between a first reference voltage Vref1 corresponding to the first slope α and a second reference voltage Vref2 corresponding to the second slope β, and
• wherein the first slope α, the second slope β, the first reference voltage Vref1, and the second reference voltage Vref2 satisfy α/β≠Vref1/Vref2.