Photoelectric conversion device

A photoelectric conversion device comprising:

• a plurality of phototransistors each comprising:
• a base region comprising a semiconductor of a first conductivity type;
• an emitter region comprising a semiconductor of a second conductivity type different from the first conductivity type;
• and
• a collector comprising semiconductor of the second conductivity type, wherein
• a photo-excited carrier is stored in said base region in a floating state,
• a junction between said emitter and base regions is forwardly biased, thereby reading a signal into the emitter side in a floating state,
• a junction between said emitter and base regions is forwardly biased for refreshment while said emitter is held at a reference potential, and
• based on the carriers stored in said base region, a current flowing between said emitter and collector regions is controlled, and
• wherein said device comprises a common substrate common to said plurality of phototransistors, a first region provided on a major surface of the common substrate, said first region having an impurity concentration lower than that of said common substrate, and a second region, provided between said plurality of base regions and on said first region, said second region having an impurity concentration higher than that of said common substrate, a part of said first region being sandwiched between said common substrate and said second region, and wherein a first potential is applied to an electrode in contact with a back side surface of said common substrate and a second potential is applied to another electrode in contact with said second region, the first and second potentials being equal to each other.