Pixel circuit of a flat panel display device and method of driving the same

摘要

A pixel circuit of a flat panel display device and a method for driving thereof are provided. The pixel circuit includes a first transistor having a first gate electrode coupled to a scan line, a second electrode coupled to a data line, a second gate electrode coupled to a controlling signal line, and a first electrode, a second transistor having a first gate electrode coupled to the first electrode of the first transistor, a second electrode coupled to a first voltage source, a second gate electrode coupled to the controlling signal line, and a first electrode, a capacitor coupled between the first gate electrode of the second transistor and the first electrode of the second transistor, and an organic light emitting diode coupled between the first electrode of the second transistor and a second voltage source, in which the threshold voltage of the first and second transistors may be controlled to the required level by supplying a controlling signal of a fixed voltage level to the second gate electrodes of the first and second transistors through the controlling signal line.

主权项

1. A pixel circuit of a flat panel display device, comprising:
a first transistor having a first gate electrode coupled to a scan line, a second electrode coupled to a data line, a second gate electrode coupled to a controlling signal line, and a first electrode; a second transistor having a first gate electrode coupled to the first electrode of the first transistor, a second electrode coupled to a first voltage source, a second gate electrode coupled to the controlling signal line, and a first electrode; a capacitor coupled between the first gate electrode of the second transistor and the first electrode of the second transistor; and an organic light emitting diode coupled between the first electrode of the second transistor and a second voltage source, wherein each of the first and second transistors further comprises:
a substrate on which the first gate electrode is located;a first insulating layer on the first gate electrode;an active layer comprising an oxide semiconductor on the first insulating layer and having at least a portion closer to the substrate than a surface of the first gate electrode facing the active layer; anda second insulating layer on and above the active layer, wherein the first electrode and the second electrode are on and above the second insulating layer and coupled with the active layer, and wherein the second gate electrode is directly on the second insulating layer and is located between the first electrode and the second electrode, wherein the controlling signal line is configured to supply a control signal to constantly maintain threshold voltages of the first and second transistors, and wherein the second transistor is configured to supply a constant current to the organic light emitting diode in response to the control signal.