PURPOSE: To facilitate the designing of a signal processing method for manufacturing a video camera, etc., and to make the device profitable as to the application of signal processing because of a digital signal by providing a sample holding circuit and an analog-to-digital converting circuit.

CONSTITUTION: In addition to the constitution of a conventional amplifying circuit, the sample holding circuit 1 and analog-to-digital converting circuit 2 are newly provided. Variation in potential by a signal is received at the gate 7 of a MOS transistor(TR) and amplified, and the signal is passed through the sample holding circuit 1 and analog-to-digital converting circuit 2 and led out of an output terminal 8 as a digital signal. Namely, a charge detection part receives the potential variation in a floating diffusion layer at the gate 7 of the MOS TR and amplifies it, then samples and holds the variation, and converts the analog signal into the digital signal, which is outputted. This device is applicable to the constitution of the charge detection part of a charge transfer device as, for example, a linear sensor.