Signal-charge detecting circuit of charge transfer device

Abstract

Abstract PURPOSE:To eliminate reset noises even if thermal noises are present in a reset transistor, by setting the concentration, the junction depth and the drain voltage of a floating diffused layer so that the floating diffused layer can be completely depleted. CONSTITUTION:In this circuit, the following parts are included: a floating diffused layer 11; a reset transistor 3, which absorbs all the signal charges in the diffused layer 11; and a source follower circuit, which detects the potential change in the floating diffused layer 11. The concentration of the floating diffused layer 11 and a reset drain voltage VRD are set so that the signal charges in the floating diffused layer 11 can be completely absorbed and the floating diffused layer 11 is completely depleted when the reset transistor 3 is conducted. Namely, the floating diffused layer 11 is not an ordinary high concentration N<+> diffused layer but a low concentration N<-> diffused layer. Therefore, the depletion layer is expanded to the side of the floating diffused layer 11 at a P-N junction between a P-type substrate 10 and the floating diffused layer 11. Thus reset noises are reduced, and a high S/N ratio is obtained.

Inventors

• 👤 Kazuo Miwata
• 👤 三輪田　和雄

Bibliographic Details