Photoelectric conversion device and imaging system

A photoelectric conversion device in which photoelectric conversion units, charge-voltage converters, transfer units, and output units are two-dimensionally arrayed, each of the charge-voltage converters converting charges into a voltage, each of the transfer units transferring charges generated in the photoelectric conversion unit to the charge-voltage converter, each of the output units outputting, to a signal line, signals corresponding to the voltage converted by the charge-voltage converter, and, in the device, for CDS processing, a first signal being output to the signal line while the charge-voltage converter has been reset, and a second signal being output to the signal line while the transfer unit has transferred charges in the photoelectric conversion unit to the charge-voltage converter, the device comprising:

• a clipping unit including a MOS transistor with a source and a drain, one of the source and the drain being connected to the signal line and the other one of the source and the drain being connected to a power supply, and the clipping unit clipping an electric potential of the signal line to an electric potential corresponding to an electric potential of the one;
• a holding capacitance, which includes a first electrode and a second electrode, the first electrode being connected to a gate of the MOS transistor, and the holding capacitance holding at least a voltage transferred to the signal line while the charge-voltage converter has been reset;
• a shift unit, which shifts an electric potential of the second electrode in a direction such that the electric potential of the second electrode comes close to a level to be transferred to the signal line while the charge-voltage converter has been reset;
• and
• a switch, which supplies a voltage on the signal line to the first electrode of the holding capacitance in a period during which the first signal is output to the signal line, and supplies a predetermined voltage to the first electrode of the holding capacitance in a period during which the second signal is output to the signal line.