Photoelectric conversion circuit and solid-state image-sensing device using it

Abstract

A photoelectric conversion circuit has: a photoelectric conversion element that produces a detection current commensurate with the amount of light received thereby; a capacitor having one end connected to one end of the photoelectric conversion element, the one end of the capacitor from which a terminal voltage commensurate with the integral of the detection current is drawn; and an amplifier that receives the terminal voltage of the capacitor and produces an amplified signal commensurate with the terminal voltage thus received. The photoelectric conversion circuit outputs a final optical signal (an output current) by using the amplified signal of the amplifier. As a current path that can serve as a charging / discharging path of the capacitor, the photoelectric conversion circuit includes only a current path along which the photoelectric conversion element is located. With this configuration, it is possible to enhance responsivity to light and improve the S / N ratio of a received optical signal by making the most of electric power obtained from a photoelectric conversion element.

Description

technical field [0001] The present invention relates to a photoelectric conversion circuit and a solid-state image sensing device using the same. Background technique [0002] FIG. 5 is a circuit diagram showing one example of a CMOS (Complementary Metal Oxide Semiconductor) photoelectric conversion circuit (so-called CMOS sensor). [0003] In the illustrated CMOS sensor, the anode of the photodiode 51 is grounded, and the cathode of the photodiode 51 is connected to one end of the switch 54 . The other end of the switch 54 is connected to one end of the capacitor 52 , the gate of the N-channel field effect transistor 53 , and one end of the switch 55 , respectively. The other end of the capacitor 52 is grounded. The other end of the switch 55 is connected to a point to which the power supply voltage Vcc is applied. The drain of the transistor 53 is connected to a point to which the power supply voltage Vcc is applied. The source of the transistor 53 is connected to one ...

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Problems solved by technology

But this does not provide a satisfactory solution and will adversely increase the device

[0019] At the same time, in the prior art of Patent Document 1, since the diffusion region (source / drain) of the field effect transistor is connected between the anode of the photodiode and the DC voltage line, the leakage of the transistor will also produce the same as above. The problem

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