Pixel current driver for organic light emitting diode displays

• US 20040129933A1
• Filed: 01/23/2004
• Published: 07/08/2004
• Est. Priority Date: 02/16/2001
• Status: Abandoned Application

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Servati, Peyman, Nathan, Arokia, Sakariya, Kapil
• Application Number:
  US10/468,319
• Publication Number:
  US 20040129933A1
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: G09G 2300/0804 Sub-multiplexed active matrix panel, i.e. wherein one active driving circuit is used at pixel level for multiple image producing elements
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H10K 19/10 comprising field-effect transistors
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

A pixel current driver comprises a plurality of thin film transistors (TFTs) each having dual gates and for driving OLED layers. A top gate of the dual gates is formed between a source and a drain of each of the thin film transistors, to thereby minimize parasitic capacitance. The top gate is grounded or electrically tied to a bottom gate. The plurality of thin film transistors may be two thin film transistors formed in voltage-programmed manner or five thin film transistors formed in a current-programmed ΔV_T-compensated manner. Other versions of the current-programmed circuit with different numbers of thin film transistors are also presented that compensate for δV_T. The OLED layer are continuous and vertically stacked on the plurality of thin film transistors to provide an aperture ratio close to 100%.

Claims

1. A pixel current driver for an organic light emitting diode (OLED) having an OLED layer for emitting light, comprising:

a plurality of thin film transistors (TFTs) each having dual gates and for driving the OLED layer, a top gate of the dual gates being formed between a source and a drain of each of the thin film transistors, to thereby minimize parasitic capacitance.

2. The pixel current driver as claimed in claim 1, wherein each of the thin film transistor is an a-Si:

H based thin film transistor.

3. The pixel current driver as claimed in claim 1, wherein each of the thin film transistor is a polysilicon-based thin film transistor.

4. The pixel current driver as claimed in claim 3, wherein each of the thin film transistors is a p-channel thin film transistor.

5. The pixel current driver as claimed in claim 2, wherein the dual gates are fabricated in a normal inverted staggered TFT structure.

6. The pixel current driver as claimed in claim 2, wherein the top gate is grounded.

7. The pixel current driver as claimed in claim 2, wherein the top gate is electrically tied to a bottom gate.

8. The pixel current driver as claimed in claim 2, wherein the plurality of thin film transistors are two thin film transistors.

9. The pixel current driver as claimed in claim 8, wherein the two thin film transistors are formed in a voltage programmed manner.

10. The pixel current driver as claimed in claim 2, wherein the plurality of thin film transistors are five thin film transistors.

11. The pixel current driver as claimed in claim 10, wherein the five thin film transistors are formed in a current-programmed Δ

V_T-compensated manner.

12. The pixel current driver as claimed in claim 2, wherein the OLED layer is continuously and vertically stacked on the plurality of thin film transistors.

13. The pixel current driver as claimed in claim 2, wherein the pixel current driver is a current mirror based pixel current driver for automatically compensating for shifts in the Vth of each of the thin film transistor in a pixel.

14. The pixel current driver as claimed in claim 10, wherein the pixel current driver is for monochrome displays.

15. The pixel current driver as claimed in claim 10, wherein the pixel current driver is for full color displays.