Photoelectric conversion device including a switch between reference voltage and a signal processing circuit

1. A photoelectric conversion device for outputting an output voltage according to incident light, comprising:

photoelectric conversion means for holding an optical charge generated by the incident light;

a signal processing circuit impressed with a reference voltage for outputting the output voltage according to the incident light by applying a predetermined process to an output signal of the photoelectric conversion means; and

a switch provided between a terminal externally supplied with the reference voltage, and the signal processing circuit.

2. A photoelectric conversion device according to claim 1 , wherein the signal processing circuit comprises:

a sample-and-hold circuit for receiving a reference signal of the photoelectric conversion means when the photoelectric conversion means is reset by a reset voltage, and an optical signal of the photoelectric conversion means according to the quantity of the optical charge in a first period and a second period, respectively, sampling the reference signal input in the first period, and holding the sampled reference signal in the second period;

a first buffer amplifier for receiving an output signal of the sample-and-hold circuit;

a second buffer amplifier for receiving the reference signal and the optical signal; and

a subtractor impressed with the reference voltage for removing a noise component of the optical signal by subtracting the sampled and held reference signal received via the first buffer amplifier from the optical signal received via the second buffer amplifier in the second period.

3. A photoelectric conversion device according to claim 1 , wherein the signal processing circuit comprises:

a first source follower circuit for receiving a reference signal of the photoelectric conversion means when the photoelectric conversion means is reset by a reset voltage;

a second source follower circuit for receiving an optical signal of the photoelectric conversion means according to a quantity of the optical charge; and

a subtractor impressed with the reference voltage for removing a noise component of the optical signal by subtracting the reference signal received via the first source follower circuit from the optical signal received via the second source follower circuit.

4. A photoelectric conversion device for outputting an output voltage according to incident light, comprising:

photoelectric conversion means for holding an optical charge generated by the incident light; and

a signal processing circuit constituted by an amplifier having a function for compulsorily turning off an output transistor impressed with a voltage according to a reference voltage, the signal processing circuit outputting the output voltage according to the incident light by applying a predetermined process to an output signal of the photoelectric conversion means.

5. A photoelectric conversion device according to claim 4 , wherein the signal processing circuit comprises:

a sample-and-hold circuit for receiving a reference signal of the photoelectric conversion means when the photoelectric conversion means is reset by a reset voltage, and an optical signal of the photoelectric conversion means according to a quantity of the optical charge in a first period and a second period, respectively, sampling the reference signal input in the first period, and holding the sampled reference signal in the second period;

a first buffer amplifier for receiving an output signal of the sample-and-hold circuit;

a second buffer amplifier, constituted by an amplifier having a function for compulsorily turning off an output transistor, for receiving the reference signal and the optical signal, and

a subtractor impressed with the reference voltage for removing a noise component of the optical signal by subtracting the sampled and held reference signal received via the first buffer amplifier from the optical signal output from the second buffer amplifier in the second period.