Photo cell and a gain control method thereof

摘要

A photocell used with an optical mouse, a CMOS sensor of a digital camera module, or a scanner includes a photo element in which a feedback circuit to maintain a base terminal voltage of the photo element constant, is not directly connected to a base terminal to control the voltage to directly maintain an emitter terminal voltage so that a stable bias voltage is generated compared to a conventional photo element. The photocell includes a stepping element to increase the voltage applied to the base terminal of the photocell, thereby improving sensitivity of the photocell and increasing effectiveness of light.