Semiconductor device and display apparatus

• US 6,954,194 B2
• Filed: 11/18/2002
• Issued: 10/11/2005
• Est. Priority Date: 04/04/2002
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Sano, Keiichi, Matsumoto, Shoichiro
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): Beck, Alexander S.
• Application Number:
  US10/298,460
• Publication Number:
  US 20030189535A1
• Time in Patent Office: 1,058 Days
• Field of Search: 345/76, 345/92, 345/205, 345/206, 345/330
• US Class Current: 345/92
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays

Abstract

A semiconductor device for individually controlling an element to be driven, such as an electroluminescence element, includes a switching TFT which operates when a selection signal is applied to its gate and which also captures a data signal, and an element-driving TFT in which its drain is connected with a drive power source, its source is connected with the element to be driven, gate receives a data signal supplied from the switching TFT, for controlling electric power supplied from the drive power source to the element to be driven. The semiconductor device further includes a storage capacitor having a first electrode connected with the switching TFT and with the gate of the element-driving TFT and a second electrode connected between the source of the element-driving TFT and the element to be driven, for holding the gate-source voltage of the element-driving TFT in accordance with the data signal, and a switching element for controlling the potential of the second electrode of the storage capacitor. With such a configuration, all the above-described switches can be formed by TFTs of the same conductivity type and reliable supply of electric power to the element to be driven can be assured.

Claims

1. A semiconductor device comprising:

a switching thin film transistor which operates when a selection signal is applied to a gate and also captures a data signal;

an element-driving thin film transistor in which a drain is connected with a drive power source, a source is connected with an element to be driven, and a gate receives a data signal supplied from the switching thin film transistor, for controlling electric power supplied from the drive power source to the element to be driven;

a storage capacitor having a first electrode connected with the switching thin film transistor and with the gate of the element-driving thin film transistor and a second electrode connected between the source of the element-driving thin film transistor and the element to be driven, for holding a gate-source voltage of the element-driving thin film transistor in accordance with the data signal; and

a switching element for controlling a potential of the second electrode of the storage capacitor.

2. A semiconductor device according to claim 1, wherein

the element-driving thin film transistor is an n-channel transistor.

3. A semiconductor device according to claim 2, wherein

the n-channel element-driving thin film transistor includes an LD region in which a low concentration of impurities is doped, between a channel region and each of source and drain regions in which a high concentration of impurities is doped.

4. A semiconductor device according to claim 3, wherein

the LD region of the n-channel element-driving transistor is made larger than an LD region of an n-channel transistor at least in a peripheral circuit.

5. A semiconductor device according to claim 1, wherein

the element to be driven is an electroluminescence element.

6. A semiconductor device according to claim 1, wherein

the switching element controls the potential of the second electrode of the storage capacitor in accordance with the ON or OFF state of the switching thin film transistor.

7. A semiconductor device according to claim 6, wherein

the switching element controls the second electrode of the storage capacitor at a fixed potential when the switching thin film transistor is ON.

8. A semiconductor device according to claim 6, wherein

the switching element controls the second electrode of the storage capacitor at the fixed potential before the switching thin film transistor is turned ON, and halts potential control for the second electrode of the storage capacitor after the switching thin film transistor is turned OFF.

9. A semiconductor device according to claim 6, wherein

the switching element is a thin film transistor and controls the potential of the second electrode of the storage capacitor in accordance with a predetermined reset signal or a selection signal supplied to the switching thin film transistor.

10. A semiconductor device according to claim 1, wherein

the switching element is connected with the source of the element-driving thin film transistor and is used for discharging, at a predetermined timing, a charge accumulated in the element to be driven.

11. A semiconductor device according to claim 1, wherein

the switching element is connected with the source of the element driving thin film transistor and is used for measuring the source potential or current of the element-driving thin film transistor connected to the element to be driven.

12. An active matrix display apparatus including a plurality of pixels arranged in a matrix, in which each pixel comprises, at least:

an element to be driven;

a switching thin film transistor which operates when a selection signal is applied to a gate and which captures a data signal;

an element-driving thin film transistor in which a drain is connected with a drive power source, a source is connected with the element to be driven, and a gate receives a data signal supplied from the switching thin film transistor, for controlling electric power supplied from the drive power source to the element to be driven;

a storage capacitor having a first electrode connected with the switching thin film transistor and with the gate of the element-driving thin film transistor and a second electrode connected between the source of the element-driving thin film transistor and the element to be driven, for holding a gate-source voltage of the element-driving thin film transistor in accordance with the data signal; and

a switching element for controlling a potential of the second electrode of the storage capacitor.

13. A display apparatus according to claim 12, wherein

the element-driving thin film transistor is an n-channel transistor.

14. A display apparatus according to claim 13, wherein

the n-channel element-driving thin film transistor includes an LD region in which a low concentration of impurities is doped, between a channel region and each of source and drain regions in which a high concentration of impurities is doped.

15. A display apparatus according to claim 14, wherein

the LD region of the n-channel element-driving transistor is made larger than an LD region of an n-channel transistor, at least in a peripheral circuit.

16. A display apparatus according to claim 12, wherein

the element to be driven is an electroluminescence element.

17. A display apparatus according to claim 12, wherein

the switching element controls the potential of the second electrode of the storage capacitor in accordance with ON and OFF of the switching thin film transistor.

18. A display apparatus according to claim 17, wherein

the switching element controls the second electrode of the storage capacitor at a fixed potential when the switching thin film transistor is ON.

19. A display apparatus according to claim 17, wherein

the switching element controls the second electrode of the storage capacitor at the fixed potential before the switching thin film transistor is turned ON, and halts potential control for the second electrode of the storage capacitor after the switching thin film transistor is turned OFF.

20. A display apparatus according to claim 17, wherein

the switching element is a thin film transistor and controls the potential of the second electrode of the storage capacitor in accordance with a predetermined reset signal or a selection signal supplied to the switching thin film transistor.

21. A display apparatus according to claim 12, wherein

the switching element is connected with the source of the element-driving thin film transistor and is used for discharging, at a predetermined timing, a charge accumulated in the element to be driven.

22. A display apparatus according to claim 12, wherein

the switching element is connected with the source of the element-driving thin film transistor and is used for measuring the source potential or current of the element-driving thin film transistor connected to the element to be driven.

23. A display apparatus including a plurality of electroluminescence elements arranged in a matrix, wherein

a driving transistor is provided corresponding to each electroluminescence element for controlling a drive current to be supplied to the electroluminescence element,

the driving transistor is an n-channel transistor and includes an LD region in which a low concentration of impurities is doped, between a channel region and each of source and drain regions in which a high concentration of impurities is doped,

a gate of the driving transistor is connected with a switching transistor and one end of a capacitor,

a connection point of the electroluminescence element and the driving transistor is connected to a low volage power source via a discharge transistor, and

the connection point of the electroluminescence element and the driving transistor is also connected with the second end of the capacitor.

24. A display apparatus including a plurality of electroluminescence element arranged in a matrix, wherein

a driving transistor is provided corresponding to each electroluminescence element for controlling a drive current to be supplied to the electroluminescence element,

the driving transistor is an n-channel transistor and includes an LD region in which a low concentration of impurities are doped, between a channel region and each of source and drain regions in which a high concentration of impurities are doped,

the LD region of the driving transistor is made larger than an LD region of an n-channel transistor at least in a perpheral circuit,

a gate of the driving transistor is connected with a switching transistor and one end of a capacitor,

a connection point of the electroluminescence element and the driving transistor is connected to a low voltage power source via a discharge transistor, and

the connection point of the electroluminescence element and the driving transistor is also connected with the other end of the capacitor.