Image capturing device and electronic apparatus
To provide an image capturing device capable of suppressing a decrease of a dynamic range of the entire image capturing device caused by an input transistor of a comparator inserted between a signal line and a load current source in an analog-digital converter. The image capturing device of the present disclosure includes: a load current source; a comparator that includes an input transistor connected between a signal line that transmits a signal read from a pixel and the load current source; and a reference signal supply section that supplies a predetermined reference signal to a charge-voltage conversion section of the pixel.
1. A light detecting device comprising:
a pixel including a floating diffusion;
a signal line configured to transmit a signal read from the pixel;
a comparator including an input transistor and a first load current source, the input transistor including a source and a drain, the source being connected to the signal line that transmits the signal read from the pixel and the drain being connected to the first load current source; and
reference signal supply circuitry configured to supply a first reference signal to the floating diffusion of the pixel.
2. The light detecting device according to claim 1 , wherein a gate of the input transistor is coupled to a ground line.
3. The light detecting device according to claim 2 , wherein the input transistor is coupled to the ground line through a coupling capacitor.
4. The light detecting device according to claim 1 , wherein the comparator further comprises an output transistor, a source of the output transistor being connected to the signal line, and a drain of the output transistor being connected to a second load current source.
5. The light detecting device according to claim 1 , wherein
the first reference signal includes a voltage with a sloping waveform that linearly changes with a predetermined slope.
6. The light detecting device according to claim 5 , wherein the predetermined slope is an upward slope.
7. The light detecting device according to claim 5 , wherein
the comparator compares a signal voltage, which is supplied through the signal line and with which the voltage with the sloping waveform overlaps, with a predetermined reference voltage.
8. The light detecting device according to claim 1 , wherein the reference signal supply circuitry is configured to supply a second reference signal to a gate of the input transistor.
9. The light detecting device according to claim 8 , wherein
the first reference signal includes a voltage with a sloping waveform that linearly changes with a predetermined slope and the second reference signal includes an offset voltage.
10. The light detecting device according to claim 1 , wherein
the floating diffusion is shared among a plurality of pixels.
11. The light detecting device according to claim 1 , wherein
the reference signal supply circuitry includes
a reference signal generator that generates the first reference signal, and
an input capacitive element that couples the first reference signal generated by the reference signal generator to the floating diffusion of the pixel.
12. The light detecting device according to claim 1 , wherein
the pixel is in a pixel array in which a plurality of pixels are arranged two dimensionally in a matrix form,
the floating diffusion is one of a plurality of floating diffusions respectively corresponding to each of the plurality of pixels, and
the reference signal supply circuitry is one of a plurality of reference signal supply circuitries that respectively supply the first reference signal to respective columns of pixels in the pixel array.
13. The light detecting device according to claim 12 , wherein
input capacitive elements are respectively provided for each pixel in a pixel column, and couple the first reference signal supplied by a corresponding reference signal supply circuitry for the pixel column to respective floating diffusions of pixels in the pixel column.
14. The light detecting device according to claim 1 , wherein
the pixel is in a pixel array in which a plurality of pixels are arranged two dimensionally in a matrix form, and
the reference signal supply circuitry is arranged common to all pixel columns of the pixel array.
15. The light detecting device according to claim 14 , wherein
for each of the pixel columns, the reference signal supply circuitry supplies the first reference signal to floating diffusions corresponding to respective pixels in respective pixel columns through a buffer circuitry.
16. The light detecting device according to claim 14 , wherein
for each of the pixel columns, the reference signal supply circuitry supplies the first reference signal to floating diffusions corresponding to respective pixels in respective pixel columns directly.
17. The light detecting device according to claim 1 , wherein
the pixel is in a pixel array in which a plurality of pixels are arranged two dimensionally in a matrix form, and
the reference signal supply circuitry is one of two reference signal supply circuitries that are arranged on each of opposite sides of the pixel array.
18. The light detecting device according to claim 17 , wherein the two reference signal supply circuitries are respectively arranged at an upper side and a lower side of the pixel array in a pixel column direction.
19. The light detecting device according to claim 17 , wherein the two reference signal supply circuitries are respectively arranged at a left side and a right side of the pixel array in a pixel row direction.
20. The light detecting device according to claim 1 , wherein
the pixel is in a pixel array in which a plurality of pixels are arranged two dimensionally in a matrix form, and
the reference signal supply circuitry is one of a plurality of reference signal supply circuitries that respectively supply the first reference signal to respective rows of pixels in the pixel array.
21. The light detecting device according to claim 14 , wherein
the reference signal supply circuitry commonly supplies the first reference signal to respective pixels in a mesh pattern in pixel units.
22. The light detecting device according to claim 15 , wherein
the reference signal supply circuitry commonly supplies the first reference signal to respective pixels in a mesh pattern in pixel units through the respective buffer circuitry corresponding to each of the columns.
23. The light detecting device according to claim 1 , wherein
the pixel is in a pixel array in which a plurality of pixels are arranged two dimensionally in a matrix form, and
the reference signal supply circuitry is arranged at a central position of the pixel array along a column direction.
24. The light detecting device according to claim 23 , wherein
the reference signal supply circuitry supplies the first reference signal to the pixels in rows above the central position through a first wiring line, and supplies the first reference signal to the pixels in rows below the central position through a second wiring line.
25. The light detecting device according to claim 1 , further comprising:
an input capacitive element configured to couple the first reference signal generated by the reference signal supply circuitry to the floating diffusion of the pixel; and
buffer circuitry configured to receive the first reference signal from the reference signal supply circuitry and provide the first reference signal to the input capacitive element, the buffer circuitry having a source follower configuration.
26. The light detecting device according to claim 25 , wherein the buffer circuitry includes an input transistor connected between a node at a predetermined potential and an input terminal of the input capacitive element.
27. The light detecting device according to claim 26 , wherein the buffer circuitry includes a constant current source transistor connected between an anode electrode of a photodiode of the pixel and the input terminal of the input capacitive element.
28. The light detecting device according to claim 1 , wherein
the light detecting device has a stacked type semiconductor chip structure formed by stacking at least two semiconductor chips, and
the pixel and the comparator are formed in different semiconductor chips, respectively.
29. The light detecting device according to claim 28 , wherein
a semiconductor chip as a first layer and a semiconductor chip as a second layer are stacked,
the pixel is formed in the semiconductor chip as the first layer, and
the comparator is formed in the semiconductor chip as the second layer.
30. The light detecting device according to claim 1 , wherein
the reference signal supply circuitry includes a reference signal generator that generates the first reference signal,
an input capacitive element couples the first reference signal generated by the reference signal generator to the floating diffusion of the pixel,
the light detecting device has a stacked type semiconductor chip structure formed by stacking at least two semiconductor chips,
the pixel is formed in a first semiconductor chip as a first layer,
the reference signal generator is formed in a second semiconductor chip as a second layer, and
the first reference signal from the reference signal generator is electrically connected to the input capacitive element through a bonding portion between the first and second layers.
31. The light detecting device according to claim 30 , wherein the bonding portion includes a Cu—Cu direct bonding.
32. The light detecting device according to claim 1 , wherein
a first semiconductor chip as a first layer, a second semiconductor chip as a second layer, and a third semiconductor chip as a third layer are stacked,
a photoelectric conversion element and a transfer transistor of the pixel are formed in the first semiconductor chip,
a constituent element of the pixel other than the photoelectric conversion element and the transfer transistor is formed in the second semiconductor chip, and
the comparator and the reference signal supply circuitry are formed in the third semiconductor chip.
33. The light detecting device according to claim 32 , wherein
the reference signal supply circuitry includes a reference signal generator that generates the first reference signal,
an input capacitive element in the second semiconductor chip receives the first reference signal through a wiring line and couples the first reference signal generated by the reference signal generator to the floating diffusion of the pixel, and
the first reference signal from the reference signal generator is electrically connected to the wiring line through a bonding portion between the second and third layers.
34. The light detecting device according to claim 33 , wherein the bonding portion includes a Cu—Cu direct bonding.
35. An electronic apparatus comprising the light detecting device according to claim 1 .