System and methods for extraction of threshold and mobility parameters in AMOLED displays
First Claim
1. A display comprising:
- a first signal line for supplying a programming voltage;
a second signal line for outputting an output voltage or current value which is a function of a parameter of at least one of the pixel circuits;
a plurality of pixel circuits, each pixel circuit comprising;
a light emitting device;
a drive transistor, controllably coupling an electrical power source to the light emitting device for supplying a controllable electrical current to the light emitting device, said drive transistor having a gate terminal, a source terminal and a drain terminal;
a first switching transistor controllably coupling the first signal line to the gate terminal of the drive transistor at a first node;
a second switching transistor controllably coupling the second signal line to one of the source and drain terminals of the drive transistor at a second node;
a storage device coupled between the first node and the second node; and
a controller coupled to each pixel circuit and configured to supply controlling input signals to the first and second switching transistors in a predetermined sequence to produce the output voltage or current value which is a function of a parameter of the pixel circuit, the sequence including;
i) turning on at least one of the first and second switching transistors to supply first and second initial voltages to the first and second nodes, respectively;
ii) turning off the second switching transistor, and connecting the electrical power source to the drive transistor so that current flows from the electrical power source to the light emitting device through the drive transistor, the magnitude of said current being controlled by the voltage applied to the gate terminal of the drive transistor discharged by the storage device; and
iii) turning on the second switching transistor and extracting a parameter of the drive transistor by reading the voltage at the second node.
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Accused Products
Abstract
A system reads a desired circuit parameter from a pixel circuit that includes a light emitting device, a drive device to provide a programmable drive current to the light emitting device, a programming input, and a storage device to store a programming signal. One embodiment of the extraction system turns off the drive device and supplies a predetermined voltage from an external source to the light emitting device, discharges the light emitting device until the light emitting device turns off, and then reads the voltage on the light emitting device while that device is turned off. The voltages on the light emitting devices in a plurality of pixel circuits may be read via the same external line, at different times.
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Citations
20 Claims
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1. A display comprising:
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a first signal line for supplying a programming voltage; a second signal line for outputting an output voltage or current value which is a function of a parameter of at least one of the pixel circuits; a plurality of pixel circuits, each pixel circuit comprising; a light emitting device; a drive transistor, controllably coupling an electrical power source to the light emitting device for supplying a controllable electrical current to the light emitting device, said drive transistor having a gate terminal, a source terminal and a drain terminal; a first switching transistor controllably coupling the first signal line to the gate terminal of the drive transistor at a first node; a second switching transistor controllably coupling the second signal line to one of the source and drain terminals of the drive transistor at a second node; a storage device coupled between the first node and the second node; and a controller coupled to each pixel circuit and configured to supply controlling input signals to the first and second switching transistors in a predetermined sequence to produce the output voltage or current value which is a function of a parameter of the pixel circuit, the sequence including; i) turning on at least one of the first and second switching transistors to supply first and second initial voltages to the first and second nodes, respectively; ii) turning off the second switching transistor, and connecting the electrical power source to the drive transistor so that current flows from the electrical power source to the light emitting device through the drive transistor, the magnitude of said current being controlled by the voltage applied to the gate terminal of the drive transistor discharged by the storage device; and iii) turning on the second switching transistor and extracting a parameter of the drive transistor by reading the voltage at the second node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating a display to produce an output voltage or current value which is a function of a parameter of the pixel circuit, the display comprising:
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a first signal line for supplying a programming voltage; a second signal line for outputting an output voltage or current value which is a function of a parameter of at least one of the pixel circuits; a plurality of pixel circuits, each pixel circuit comprising; a light emitting device; a drive transistor, controllably coupling an electrical power source to the light emitting device for supplying a controllable electrical current to the light emitting device, said drive transistor having a gate terminal, a source terminal and a drain terminal; a first switching transistor controllably coupling the first signal line to the gate terminal of the drive transistor at a first node; a second switching transistor controllably coupling the second signal line to one of the source and drain terminals of the drive transistor at a second node; a storage device coupled between the first node and the second node; and a controller coupled to each pixel circuit and capable of supplying controlling input signals to the first and second switching transistors in a predetermined sequence to produce the output voltage or current value which is a function of the parameter of the pixel circuit, the method comprising; i) turning on at least one of the first and second switching transistors to supply first and second initial voltage to the first and second nodes, respectively; ii) turning off the second switching transistor, and connecting the electrical power source to the drive transistor so that current flows from the electrical power source to the light emitting device through the drive transistor, the magnitude of said current being controlled by the voltage applied to the gate terminal of the drive transistor discharged by the storage device; and iii) turning on the second switching transistor and extracting the parameter of the drive transistor by reading the voltage at the second node. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification