Imaging device and method of driving imaging device

1. An imaging device comprising:

a plurality of pixels which are arranged to form a plurality of columns and each of which includes a photoelectric conversion unit that generates charges by photoelectric conversion;

a plurality of column circuits which are provided to the plurality of columns, respectively, and each of which receives a signal from a part of the plurality of pixels;

a first common control line connected to each of the plurality of column circuits; and

a control unit that controls the plurality of column circuits,

wherein each of the plurality of column circuits includes an amplifier circuit whose gain is switchable and a first transistor that controls a current flowing in the amplifier circuit, and

wherein the control unit controls the column circuit so that the first transistor supplies a current of a first current value when the amplifier circuit is at a first gain and the first transistor supplies a current of a second current value which is smaller than the first current value when the amplifier circuit is at a second gain which is larger than the first gain.

2. The imaging device according to claim 1 , wherein the control unit supplies a bias voltage to the first transistor via the first common control line, and controls a current value of a current supplied by the first transistor by changing the bias voltage.

3. The imaging device according to claim 2 , wherein each of the plurality of column circuits further includes a first sample and hold circuit that holds the bias voltage supplied to the first transistor.

4. The imaging device according to claim 1 further comprising a second common control line connected to each of the plurality of column circuits,

wherein each of the plurality of column circuits further includes a second transistor connected to the first transistor in a cascade configuration and controlled by a bias voltage supplied from the second common control line.

5. The imaging device according to claim 4 , wherein each of the plurality of column circuits further includes a second sample and hold circuit that holds the bias voltage supplied to the second transistor.

6. The imaging device according to claim 4 further comprising a third common control line connected to each of the plurality of column circuits,

wherein each of the plurality of column circuits further includes a third transistor connected to the second transistor in a cascade configuration and controlled by a bias voltage supplied from the third common control line.

7. The imaging device according to claim 1 ,

wherein each of the plurality of column circuits includes an input capacitor in which a plurality of capacitance values are selectable and a feedback capacitor in which a plurality of capacitance values are selectable, and

wherein the first gain is switched to or from the second gain by changing a ratio of a capacitance value of the input capacitor and a capacitance value of the feedback capacitor.

8. The imaging device according to claim 2 ,

wherein a first bias voltage Vα 1 is supplied to a gate of the first transistor when the amplifier circuit is at the first gain,

wherein a second bias voltage Vα 2 is supplied to the gate of the first transistor when the amplifier circuit is at the second gain, and

wherein the control unit controls the bias voltage supplied to the first transistor so that the first bias voltage Vα 1 , the second bias voltage Vα 2 , and a source voltage VD of the first transistor satisfy a relationship of (VD-Vα 2 )<(VD-Vα 1 ).

9. The imaging device according to claim 1 , wherein the amplifier circuit is a common source circuit.

10. The imaging device according to claim 1 , wherein the amplifier circuit is a one-input, one-output circuit.

11. An imaging system comprising:

the imaging device according to claim 1 ; and

a signal processing unit that processes a signal output from the imaging device.

12. A movable object comprising:

the imaging device according to claim 1 ;

a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals output from the pixels of the imaging device; and

a control unit that controls the movable object based on the distance information.

13. A method of driving an imaging device including a plurality of pixels which are arranged to form a plurality of columns and each of which includes a photoelectric conversion unit that generates charges by photoelectric conversion, a plurality of column circuits which are provided to the plurality of columns, respectively, and each of which receives a signal from a part of the plurality of pixels, and a first common control line connected to each of the plurality of column circuits, wherein each of the plurality of column circuits includes an amplifier circuit whose gain is switchable and a first transistor that controls a current flowing in the amplifier circuit, the method comprising:

switching the bias voltage to be supplied to the first transistor of each of the plurality of column circuits via the first common control line in accordance with a gain of the amplifier circuit,

wherein the bias voltage is controlled so that the first transistor supplies a current of a first current value when the amplifier circuit is at a first gain and the first transistor supplies a current of a second current value which is smaller than the first current value when the amplifier circuit is at a second gain which is larger than the first gain.