Thin film transistor circuit and semiconductor display device using the same

• US 6,268,842 B1
• Filed: 04/09/1999
• Issued: 07/31/2001
• Est. Priority Date: 04/13/1998
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei
• Primary Examiner(s): Lao, Lun-Yi
• Application Number:
  US09/289,306
• Time in Patent Office: 844 Days
• Field of Search: 345/98, 345/100, 345/87, 345/204, 345/205, 345/206, 330/253, 330/257, 330/288, 330/252, 315/169--16
• US Class Current: 345/98
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H03F 2203/45371 the AAC comprising parallel coupled multiple transistors at their source and gate and drain or at their base and emitter and collector, e.g. in a cascode dif amp, only those forming the composite common source transistor or the composite common emitter transistor respectively
• CPC Class Codes: H03F 2203/45674 the LC comprising one current mirror
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence

Abstract

There is provided a thin film transistor circuit used for a driver circuit for providing a semiconductor display device without a picture blur and with high fineness/high resolution. In the thin film transistor circuit, a TFT having a large size (channel width) is not used, but a plurality of TFTs each having a small size are connected in parallel to each other and are used. By this, while sufficient current capacity of the thin film transistors is secured, fluctuation in the characteristics can be decreased.

Claims

1. A semiconductor device comprising at least:

a differential circuit including x (x is a natural number not less than

     2) input-side thin film transistors which have a common gate electrode potential and to which a signal is inputted, and x output-side thin film transistors which have a common gate electrode potential and from which a signal is outputted; and

a current mirror circuit including y (y is a natural number not less than

     2) input-side thin film transistors and y output-side thin film transistors, which have a common gate electrode potential, the gate electrodes of y input-side thin film transistors being connected to sources/drains of y input-side thin film transistors.

2. A device according to claim 1 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

3. A device according to claim 1 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over a substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

4. A device according to claim 1 wherein said semiconductor device is an active matrix type liquid crystal display device.

5. A device according to claim 1 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.

6. A semiconductor device comprising at least:

a differential circuit including x (x is a natural number not less than

     2) input-side thin film transistors which have a common gate electrode potential and to which a signal is inputted, and (n n x) (n is a natural number not less than

     2) output-side thin film transistors which have a common gate electrode potential and from which a signal is outputted; and

a current mirror circuit including y (y is a natural number not less than

     2) input-side thin film transistors and (n n y) output-side thin film transistors, which have a common gate electrode potential, the gate electrodes of y input-side thin film transistors being connected to source/drain regions of y input-side thin film transistors.

7. A device according to claim 6 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

8. A device according to claim 6 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over a substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

9. A device according to claim 6 wherein said semiconductor device is an active matrix type liquid crystal display device.

10. A device according to claim 6 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.

11. A semiconductor device comprising:

a pixel matrix region; and

a driver circuit comprising at least a thin film transistor circuit, the thin film transistor circuit comprising;

a differential circuit including x (x is a natural number not less than

     2) input-side thin film transistors which have a common gate electrode potential and to which a signal is inputted, and x output-side thin film transistors which have a common gate electrode potential and from which a signal is outputted; and

a current mirror circuit including y (y is a natural number not less than

     2) input-side thin film transistors and y output-side thin film transistors, which have a common gate electrode potential, the gate electrodes of y input-side thin film transistors being connected to source/drain regions of y input-side thin film transistors,

wherein the pixel matrix region and the driver circuit are formed on the same substrate.

12. A device according to claim 11 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

13. A device according to claim 11 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over said substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

14. A device according to claim 11 wherein said semiconductor device is an active matrix type liquid crystal display device.

15. A device according to claim 11 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.

16. A semiconductor device comprising:

a pixel matrix region; and

a driver circuit comprising at least a thin film transistor circuit, the thin film transistor circuit comprising at least;

a differential circuit including x (x is a natural number not less than

     2) input-side thin film transistors which have a common gate electrode potential and to which a signal is inputted, and (n n x) (n is a natural number not less than

     2) output-side thin film transistors which have a common gate electrode potential and from which a signal is outputted; and

a current mirror circuit including y (y is a natural number not less than

     2) input-side thin film transistors and (n×

y) output-side thin film transistors, which have a common gate electrode potential, the gate electrodes of y input-side thin film transistors are connected to source/drain regions of y input-side thin film transistors,

wherein the pixel matrix region and the driver circuit are formed on the same substrate.

17. A device according to claim 16 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

18. A device according to claim 16 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over said substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

19. A device according to claim 16 wherein said semiconductor device is an active matrix type liquid crystal display device.

20. A device according to claim 16 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.

21. A semiconductor device comprising a pixel matrix region and a driver circuit having at least one buffer circuit, said buffer circuit comprising:

a differential circuit having x input-side thin film transistors connecting in parallel to each other (x≧

2, x is natural number) and n×

x output-side thin film transistors connecting in parallel to each other (n≧

1, n is natural number), and

a current mirror circuit having y input-side thin film transistors connecting in parallel to each other (y≧

2, y is natural number) and n×

y output-side thin film transistors connecting in parallel to each other (n≧

1, n is natural number).

22. A device according to claim 21 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

23. A device according to claim 21 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over said substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

24. A device according to claim 21 wherein said semiconductor device is an active matrix type liquid crystal display device.

25. A device according to claim 21 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.

26. A semiconductor device comprising a pixel matrix region and a driver circuit having at least one buffer circuit, said buffer circuit comprising:

a differential circuit having a plurality of thin film transistors connecting in parallel to each other and dividing an input into x and a plurality of thin film transistors connecting in parallel to each other and dividing an output into n×

x (n≧

1, n is natural number), respectively, and

a current mirror circuit having a plurality of thin film transistors connecting in parallel to each other and dividing an input into y and a plurality of thin film transistors connecting in parallel to each other and dividing an output into n×

y (n≧

1, n is natural number), respectively.

27. A device according to claim 26 wherein said thin film transistors in said different circuit are different conductivity type from said thin film transistors in said current mirror circuit.

28. A device according to claim 26 wherein each of said thin film transistors in said differential circuits and said mirror circuit comprises:

a crystalline semiconductor film over said substrate having an insulating surface, said crystalline semiconductor film having at least a channel and said source/drain; and

said gate electrode adjacent to said crystalline semiconductor film with a gate insulating film interposed therebetween,

wherein width of said channel is 100 μ

m or less.

29. A device according to claim 26 wherein said semiconductor device is an active matrix type liquid crystal display device.

30. A device according to claim 26 wherein said semiconductor device is selected from the group consisting of a video camera, a still camera, a rear type projector, a front type projector, a head mount display, a car navigation system, a portable telephone, a mobile computer, and a personal computer.