Image sensors comprising photodiodes and image processing devices including the same

1. An image sensor, comprising:

a photodiode configured to convert an optical signal into photogenerated charge;

a sensing node adjacent to the photodiode and configured to sense the photogenerated charge;

a read-out circuit configured to convert the photogenerated charge into an electrical signal and to output the electrical signal through an output line; and

at least one capacitor formed between the sensing node and a conversion gain control line;

wherein the conversion gain control line corresponding to the at least one capacitor is selectively connected to a ground line or the output line based on at least one control signal.

2. The image sensor of claim 1 , wherein the read-out circuit comprises:

a drive transistor configured to operate as a source follower amplifier having an output of the sensing node as an input; and

a select transistor connected in series between a source terminal of the source follower amplifier and the output line.

3. The image sensor of claim 1 , wherein the conversion gain control line is separated from the output line, and

wherein the conversion gain control line is configured to surround the sensing node.

4. The image sensor of claim 1 , further comprising:

at least two capacitors;

wherein the sensing node is horizontally between a first conversion gain control line and a second conversion gain control line, which are separated from the output line,

wherein a first capacitor of the at least two capacitors is formed between the first conversion gain control line and the sensing node, and

wherein a second capacitor of the at least two capacitors is formed between the sensing node and the second conversion gain control line.

5. The image sensor of claim 1 , further comprising:

at least two capacitors;

wherein a first conversion gain control line is separated from the output line and is configured to surround the sensing node,

wherein a second conversion gain control line is stacked on the first conversion gain control line,

wherein a first capacitor of the at least two capacitors is formed between the first conversion gain control line and the sensing node, and

wherein a second capacitor of the at least two capacitors is formed between the sensing node and the second conversion gain control line.

6. The image sensor of claim 1 , further comprising:

a switch configured to be connected between the conversion gain control line and a power supply voltage, and to connect the conversion gain control line to the power supply voltage based on a boosting control signal;

wherein when the conversion gain control line is connected to the ground line, a voltage at the sensing node is increased based on the boosting control signal by a boosting voltage corresponding to the power supply voltage.

7. The image sensor of claim 6 , wherein when the conversion gain control line is connected to the output line, the voltage at the sensing node is increased based on the boosting control signal by a boosting voltage corresponding to a reset voltage.

8. An image sensor, comprising:

a pixel array comprising a plurality of pixels;

a timing controller configured to control operation of the pixel array and to generate at least one control signal for controlling an output of each of the pixels; and

a switching circuit comprising a plurality of switches corresponding to a plurality of column lines comprised in the pixel array to adjust a conversion gain of pixels corresponding to each of the columns based on the at least one control signal;

wherein each pixel comprises:

a photodiode configured to convert an optical signal into photogenerated charge;

a sensing node adjacent to the photodiode and configured to sense the photogenerated charge;

a read-out circuit configured to convert the photogenerated charge into an electrical signal and to output the electrical signal through an output line; and

at least one capacitor formed between the sensing node and a conversion gain control line; and

wherein the switching circuit is configured to selectively control connection of the conversion gain control line.

9. The image sensor of claim 8 , wherein the read-out circuit comprises:

a drive transistor configured to operate as a source follower amplifier having an output of the sensing node as an input; and

a select transistor connected in series between a source terminal of the source follower amplifier and the output line.

10. The image sensor of claim 8 , wherein the conversion gain control line corresponding to the at least one capacitor is selectively connected to a ground line or the output line based on the at least one control signal.

11. An image processing device, comprising:

the image sensor of claim 8 ; and

a processor configured to control operation of the image sensor.

12. The image processing device of claim 11 , wherein the image processing device includes one or more of a mobile phone, a tablet personal computer (PC), and a digital single-lens reflex (DSLR) camera.

13. An image sensor, comprising:

a photodiode configured to convert an optical signal into photogenerated charge;

a sensing node configured to sense the photogenerated charge;

a read-out circuit configured to convert the photogenerated charge into an electrical signal and to output the electrical signal; and

one or more capacitors between the sensing node and one or more conversion gain control lines;

wherein the one or more conversion gain control lines corresponding to the one or more capacitors are selectively connected to a ground line or an output line based on one or more control signals.

14. The image sensor of claim 13 , wherein a first conversion gain control line corresponding to a first capacitor is selectively connected to the ground line or the output line based on a first control signal, and

wherein a second conversion gain control line corresponding to a second capacitor is selectively connected to the ground line or the output line based on a second control signal.

15. The image sensor of claim 13 , further comprising:

at least two capacitors;

wherein the sensing node is between a first conversion gain control line and a second conversion gain control line,

wherein the first conversion gain control line is separated from the output line,

wherein the second conversion gain control line is separated from the output line,

wherein a first capacitor of the at least two capacitors is between the sensing node and the first conversion gain control line, and

wherein a second capacitor of the at least two capacitors is between the sensing node and the second conversion gain control line.

16. The image sensor of claim 15 , wherein the first conversion gain control line is on a first side of the sensing node,

wherein the second conversion gain control line is on a second side of the sensing node, and

wherein the first side of the sensing node is opposite to the second side of the sensing node.

17. The image sensor of claim 15 , wherein a first portion of the first conversion gain control line is on a first side of the sensing node,

wherein a second portion of the first conversion gain control line is on a second side of the sensing node,

wherein the second conversion gain control line is on a third side of the sensing node, and

wherein the first side of the sensing node is opposite to the second side of the sensing node.

18. A computing system comprising the image sensor of claim 13 .

19. An image processing device comprising the image sensor of claim 13 .

20. A camera system comprising the image sensor of claim 13 .