Solid-state imaging device and imaging apparatus

1. A solid-state imaging device comprising:

a plurality of pixel cells arranged in rows and columns, each of the pixel cells including a photoelectric conversion element that generates a signal charge according to an amount of light received and an amplifying transistor that generates a signal voltage by amplifying the signal charge;

a plurality of vertical signal lines each of which is provided for a corresponding one of the columns and to each of which are output the signal voltages generated by pixel cells included in the plurality of pixel cells that are disposed in a corresponding one of the columns; and

a plurality of column circuits each of which is provided for a corresponding one or more of the columns and into each of which are input the signal voltages output to one or more of the vertical signal lines disposed in the corresponding one or more of the columns,

wherein each of the plurality of column circuits includes

an amplifier into which input signals based on the signal voltages are input and that includes a constant current source transistor,

the solid-state imaging device further comprises

a reference current source circuit that supplies a first bias voltage to gates of a plurality of the constant current source transistors included in the plurality of column circuits, and

each of the plurality of column circuits further includes

a sample-and-hold circuit that holds the first bias voltage.

2. The solid-state imaging device according to claim 1 ,

wherein each of the plurality of column circuits includes an AD conversion unit configured to convert the signal voltages into digital signals,

the AD conversion unit includes a comparator that compares the signal voltages with a reference signal,

the amplifier is an amplifier that is included in the comparator and into which the signal voltages and the reference signal are input, and

the sample-and-hold circuit holds the first bias voltage during a period in which the comparator compares the reference signal and one of the signal voltages.

3. The solid-state imaging device according to claim 2 ,

wherein the amplifier includes:

a differential amplifier that compares the signal voltages with the reference signal; and

an amplifying amplifier that includes the constant current source transistor and amplifies an output signal of the differential amplifier, and

the sample-and-hold circuit holds the first bias voltage during a period in which the differential amplifier compares the reference signal and the one of the signal voltages.

4. The solid-state imaging device according to claim 2 ,

wherein the sample-and-hold circuit samples the first bias voltage outside the period in which the comparator compares the reference signal and the one of the signal voltages.

5. The solid-state imaging device according to claim 1 ,

wherein each of the plurality of column circuits includes a signal amplifier that includes the amplifier and amplifies one of the signal voltages, and

the sample-and-hold circuit holds the first bias voltage during a period in which the signal amplifier amplifies the one of the signal voltages.

6. The solid-state imaging device according to claim 5 ,

wherein the sample-and-hold circuit samples the first bias voltage outside the period in which the signal amplifier amplifies the one of the signal voltages.

7. The solid-state imaging device according to claim 1 ,

wherein the sample-and-hold circuit includes:

a sample-and-hold transistor connected between the gate of the constant current source transistor and the reference current source circuit; and

a sample-and-hold capacitor connected to the gate of the constant current source transistor.

8. The solid-state imaging device according to claim 1 ,

further comprising

a bias line connected to the reference current source circuit; and a plurality of the sample-and-hold circuits included in the plurality of column circuits,

wherein the reference current source circuit supplies the first bias voltage to the gates of the plurality of constant current source transistors via the bias line.

9. The solid-state imaging device according to claim 8 ,

wherein the reference current source circuit includes:

a transistor that forms a current mirror circuit together with each of the constant current source transistors; and

a reference current source that supplies a reference current to the transistor.

10. The solid-state imaging device according to claim 1 ,

wherein the reference current source circuit includes a plurality of first reference current source units each of which is provided for a corresponding one of the column circuits, and

each of the plurality of first reference current source units includes:

a current mirror transistor that forms a current mirror circuit together with the constant current source transistor and supplies the first bias voltage to the gate of the constant current source transistor; and

a reference current source transistor that supplies a reference current to the current mirror transistor.

11. The solid-state imaging device according to claim 10 ,

wherein the reference current source circuit further includes:

a bias line connected to gates of a plurality of the reference current source transistors included in the plurality of first reference current source units; and

a second reference current source unit configured to supply a second bias voltage to the gates of the plurality of reference current source transistors via the bias line.

12. The solid-state imaging device according to claim 1 ,

wherein the amplifier is a grounded-source amplifier.

13. The solid-state imaging device according to claim 1 ,

wherein the column circuits each further include a power-down control unit configured to stop the amplifier.

14. An imaging apparatus comprising the solid-state imaging device according to claim 1 .