PHOTOELECTRIC CONVERSION DEVICE AND METHOD FOR OPERATING THE SAME

• US 20120104238A1
• Filed: 10/20/2011
• Published: 05/03/2012
• Est. Priority Date: 10/29/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: HIROSE, Atsushi
• Granted Patent: US 9,209,209 B2
• Time in Patent Office: Days
• US Class Current: 250/214.R
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors

Abstract

To provide a photoelectric conversion device with low power consumption and a method for operating the photoelectric conversion device. The photoelectric conversion device includes a charge storage capacitor portion, a photodiode, and a plurality of transistors. The charge storage capacitor portion is charged after being reset. Then, the charge storage capacitor portion is discharged through the photodiode or a current mirror circuit connected to the photodiode for a given period of time, and after that, the potential of the charge storage capacitor portion is read. Since power is consumed only at the time of charging, power consumption can be reduced.

Claims

1. A photoelectric conversion device comprising:

a photodiode;

a first transistor;

a second transistor;

a third transistor;

a charge storage capacitor portion; and

a first terminal, a second terminal, a third terminal, a fourth terminal, a fifth terminal, and a sixth terminal,

wherein one of electrodes of the charge storage capacitor portion is electrically connected to a source electrode of the first transistor, a drain electrode of the second transistor, a drain electrode of the third transistor, and the sixth terminal,

wherein the other of the electrodes of the charge storage capacitor portion is electrically connected to an anode of the photodiode, a source electrode of the third transistor, and the second terminal,

wherein a source electrode of the second transistor is electrically connected to a cathode of the photodiode,

wherein a drain electrode of the first transistor is electrically connected to the first terminal,

wherein a gate electrode of the first transistor is electrically connected to the third terminal,

wherein a gate electrode of the second transistor is electrically connected to the fourth terminal, and

wherein a gate electrode of the third transistor is electrically connected to the fifth terminal.

2. The photoelectric conversion device according to claim 1,

wherein the first to third transistors comprise an oxide semiconductor.

3. The photoelectric conversion device according to claim 1,

wherein the first terminal is electrically connected to a high potential power supply,

wherein the second terminal is electrically connected to a low potential power supply,

wherein the third to fifth terminals are signal input terminals, and

wherein the sixth terminal is a signal output terminal.

4. The photoelectric conversion device according to claim 1,

wherein the first to third transistors are n-channel transistors.

5. The photoelectric conversion device according to claim 1,

wherein the first transistor is a p-channel transistor, and

wherein the second transistor and the third transistor are n-channel transistors.

6. A photoelectric conversion device comprising:

a photodiode;

a first transistor;

a second transistor;

a third transistor;

a current mirror circuit including a fourth transistor and a fifth transistor;

a charge storage capacitor portion; and

a first terminal, a second terminal, a third terminal, a fourth terminal, a fifth terminal, and a sixth terminal,

wherein one of electrodes of the charge storage capacitor portion is electrically connected to a source electrode of the first transistor, a drain electrode of the second transistor, a drain electrode of the third transistor, and the sixth terminal,

wherein the other of the electrodes of the charge storage capacitor portion is electrically connected to a source electrode of the third transistor, a source electrode of the fourth transistor, a source electrode of the fifth transistor, and the second terminal,

wherein a source electrode of the second transistor is electrically connected to a drain electrode of the fifth transistor,

wherein a drain electrode of the first transistor is electrically connected to a cathode of the photodiode and the first terminal,

wherein a drain electrode of the fourth transistor is electrically connected to an anode of the photodiode, a gate electrode of the fourth transistor, and a gate electrode of the fifth transistor,

wherein a gate electrode of the first transistor is electrically connected to the third terminal,

wherein a gate electrode of the second transistor is electrically connected to the fourth terminal, and

wherein a gate electrode of the third transistor is electrically connected to the fifth terminal.

7. The photoelectric conversion device according to claim 6,

wherein the first to fifth transistors comprise an oxide semiconductor.

8. The photoelectric conversion device according to claim 6,

wherein the first terminal is electrically connected to a high potential power supply,

wherein the second terminal is electrically connected to a low potential power supply,

wherein the third to fifth terminals are signal input terminals, and

wherein the sixth terminal is a signal output terminal.

9. The photoelectric conversion device according to claim 6,

wherein the first to third transistors are n-channel transistors.

10. The photoelectric conversion device according to claim 6,

wherein the first transistor is a p-channel transistor, and

wherein the second transistor and the third transistor are n-channel transistors.

11. The photoelectric conversion device according to claim 6, further comprising a sixth transistor connected in parallel with the fourth transistor.

12. The photoelectric conversion device according to claim 11,

wherein the source electrode and the drain electrode of the fifth transistor are electrically connected to a source electrode and a drain electrode of the sixth transistor, respectively.

13. A method for operating a photoelectric conversion device,

wherein one of electrodes of a charge storage capacitor portion is electrically connected to a source electrode of a first transistor, a drain electrode of a second transistor, a drain electrode of a third transistor, and a sixth terminal,

wherein the other of the electrodes of the charge storage capacitor portion is electrically connected to an anode of a photodiode, a source electrode of the third transistor, and a second terminal,

wherein a source electrode of the second transistor is electrically connected to a cathode of the photodiode,

wherein a drain electrode of the first transistor is electrically connected to a first terminal;

wherein a gate electrode of the first transistor is electrically connected to a third terminal,

wherein a gate electrode of the second transistor is electrically connected to a fourth terminal; and

wherein a gate electrode of the third transistor is electrically connected to a fifth terminal,

the method comprising the steps of;

setting the first terminal at a high power supply potential and the second terminal at a low power supply potential,

supplying a first potential for turning on the third transistor to the fifth terminal to discharge the charge storage capacitor portion,

supplying a second potential for turning off the third transistor to the fifth terminal after supplying the first potential,

supplying a third potential for turning on the first transistor to the third terminal to charge the charge storage capacitor portion,

supplying a fourth potential for turning off the first transistor to the third terminal after supplying the third potential,

supplying a fifth potential for turning on the second transistor to the fourth terminal to discharge the charge storage capacitor portion through the photodiode,

supplying a sixth potential for turning off the second transistor to the fourth terminal after supplying the fifth potential, and

reading a seventh potential of the charge storage capacitor portion through the sixth terminal as a signal.

14. The photoelectric conversion device according to claim 13,

wherein the first to third transistors comprise an oxide semiconductor.

15. The photoelectric conversion device according to claim 13,

wherein the first terminal is electrically connected to a high potential power supply,

wherein the second terminal is electrically connected to a low potential power supply,

wherein the third to fifth terminals are signal input terminals, and

wherein the sixth terminal is a signal output terminal.

16. The photoelectric conversion device according to claim 13,

wherein the first to third transistors are n-channel transistors.

17. The photoelectric conversion device according to claim 13,

wherein the first transistor is a p-channel transistor, and

wherein the second transistor and the third transistor are n-channel transistors.

18. A method for operating a photoelectric conversion device,

wherein one of electrodes of a charge storage capacitor portion is electrically connected to a source electrode of a first transistor, a drain electrode of a second transistor, a drain electrode of a third transistor, and a sixth terminal,

wherein the other of the electrodes of the charge storage capacitor portion is electrically connected to a source electrode of the third transistor, a source electrode of a fourth transistor, a source electrode of a fifth transistor, and a second terminal,

wherein a source electrode of the second transistor is electrically connected to a drain electrode of the fifth transistor;

a drain electrode of the first transistor is electrically connected to a cathode of a photodiode and a first terminal,

wherein a drain electrode of the fourth transistor is electrically connected to an anode of the photodiode, a gate electrode of the fourth transistor, and a gate electrode of the fifth transistor;

a gate electrode of the first transistor is electrically connected to a third terminal, and

wherein a gate electrode of the second transistor is electrically connected to a fourth terminal; and

a gate electrode of the third transistor is electrically connected to a fifth terminal,

the method comprising the steps of;

setting the first terminal at a high power supply potential and the second terminal at a low power supply potential;

supplying a first potential for turning on the third transistor to the fifth terminal to discharge the charge storage capacitor portion;

supplying a second potential for turning off the third transistor to the fifth terminal after supplying the first potential;

supplying a third potential for turning on the first transistor to the third terminal to charge the charge storage capacitor portion;

supplying a fourth potential for turning off the first transistor to the third terminal after supplying the third potential;

supplying a fifth potential for turning on the second transistor to the fourth terminal to discharge the charge storage capacitor portion through the fifth transistor;

supplying a sixth potential for turning off the second transistor to the fourth terminal; and

reading a seventh potential of the charge storage capacitor portion through the sixth terminal as a signal.

19. The photoelectric conversion device according to claim 18,

wherein the first to fifth transistors comprise an oxide semiconductor.

20. The photoelectric conversion device according to claim 18,

wherein the first terminal is electrically connected to a high potential power supply,

wherein the second terminal is electrically connected to a low potential power supply,

wherein the third to fifth terminals are signal input terminals, and

wherein the sixth terminal is a signal output terminal.

21. The photoelectric conversion device according to claim 18,

wherein the first to third transistors are n-channel transistors.

22. The photoelectric conversion device according to claim 18,

wherein the first transistor is a p-channel transistor, and

wherein the second transistor and the third transistor are n-channel transistors.

23. The photoelectric conversion device according to claim 18, further comprising a sixth transistor connected in parallel with the fourth transistor.

24. The photoelectric conversion device according to claim 23,

wherein the source electrode and the drain electrode of the fifth transistor are electrically connected to a source electrode and a drain electrode of the sixth transistor, respectively.