Solid-state imaging device and method of driving solid-state imaging device

A method of driving a solid-state imaging device having a photoelectric conversion unit that generates charges by photoelectric conversion and an amplifier unit that comprises an input node, the method comprising:

• setting a voltage of the input node to a first voltage by using logarithmic compression to convert a current generated by charges overflowing from the photoelectric conversion unit to the input node into a voltage corresponding to the current;
• transferring charges from the photoelectric conversion unit to the input node;
• setting a voltage of the input node to a second voltage by converting the charges transferred to the input node into a voltage corresponding to the charges;
• at the amplifier unit, outputting a first signal based on the first voltage and a second signal based on the second voltage;
• performing the logarithmic compression by using a MOS transistor connected to the input node;
• and
• acquiring, as a reference signal for the first signal, an output of the amplifier unit when the input node is set to a third voltage defined in accordance with a threshold voltage of the MOS transistor when the MOS transistor operates in a sub-threshold region.

A solid-state imaging device comprising:

• a photoelectric conversion unit that generates charges by photoelectric conversion;
• a transfer unit connected to the photoelectric conversion unit;
• an amplifier unit having an input node connected to the transfer unit;
• a logarithmic compression conversion unit connected to the input node;
• and a charge-to-voltage conversion unit connected to the input node,
• wherein when a current generated by charges overflowing from the photoelectric conversion unit to the input node with the transfer unit being not conductive is converted into a voltage corresponding to the current by logarithmic compression performed by the logarithmic compression conversion unit, a voltage of the input node is a first voltage,
• wherein when charges transferred from the photoelectric conversion unit to the input node in response to conduction of the transfer unit are converted into a voltage corresponding to the charges by the charge-to-voltage conversion unit, a voltage of the input node is a second voltage,
• wherein the amplifier unit outputs a first signal based on the first voltage and a second signal based on the second voltage,
• wherein the logarithmic compression conversion unit includes a diode connected to the input node, and
• wherein the first voltage is a voltage corresponding to a voltage of the input node that changes due to the current flowing to the diode whose operational point is set in a sub-threshold region.