Importance

Loading Importance Indicators...

Abstract

When a photodiode receives light, it produces a charge corresponding to the intensity of light, and outputs it as a current signal. The current signal is input to an integral circuit constituted by a feedback capacitive element and a charge amplifier, and is integrated by time. On the other hand, a step charge generator generates a charge corresponding to one of reference voltage levels +Vref and -Vref in response to first and second clock signals CLK1 and CLK2, and supplies the charge to the feedback capacitive element in synchronism with the clock signal. The integral circuit executes an integral operation by accumulating the charge produced by the photodiode, and supplies a step charge, thus executing .SIGMA..DELTA. modulation. An AD conversion result is obtained from the .SIGMA..DELTA. modulation result. In this manner, high-precision digital data is output in correspondence with the intensity of light by the photodiode with a simple circuit arrangement.

Loading the Abstract Image...

First Claim