Pixel driver circuit with load-balance in current mirror circuit
First Claim
1. A pixel drive circuit for use in a display, the pixel drive circuit comprising:
- switching circuitry for providing a reference current input;
a current mirror for providing a drive current to a light emitting device based on the reference current, the current mirror including;
a drive thin film transistor for conveying the drive current through the light emitting device, the drive thin film transistor being connected in series with the light emitting device;
a reference thin film transistor for receiving the reference current, the reference thin film transistor having a gate connected to a gate of the drive transistor, the reference thin film transistor having a reference node coupled to a biasing potential for balancing the current mirror, wherein a first node of the drive thin film transistor corresponding to the reference node is not connected to the biasing potential, thereby preventing a mismatch between the reference thin film transistor and the drive thin film transistor over time; and
a capacitor for storing a program voltage independent of a transistor threshold voltage, the program voltage settling on the capacitor while the reference current is conveyed through the reference thin film transistor, the capacitor having a terminal coupled to both the gate of the drive thin film transistor and the gate of the reference thin film transistor.
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Accused Products
Abstract
A pixel circuit for use in a display comprising a plurality of pixels is provided. The load-balanced current mirror pixel circuit can compensate for device degradation and/or mismatch, and changing environmental factors like temperature and mechanical strain. The pixel circuit comprises a pixel drive circuit comprising, switching circuitry, a current mirror having a reference transistor and a drive transistor, the reference transistor and the drive transistor each having a first and second node and a gate, the gate of the reference transistor being connected to the gate of the drive transistor; and a capacitor connected between the gate of the reference transistor and a ground potential, and a load connected between the current mirror and a ground potential, the load having a first load element and a second load element, the first load element being connected to the first node of the reference transistor and the second load element being connected to the first node of the drive transistor.
84 Citations
18 Claims
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1. A pixel drive circuit for use in a display, the pixel drive circuit comprising:
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switching circuitry for providing a reference current input; a current mirror for providing a drive current to a light emitting device based on the reference current, the current mirror including; a drive thin film transistor for conveying the drive current through the light emitting device, the drive thin film transistor being connected in series with the light emitting device; a reference thin film transistor for receiving the reference current, the reference thin film transistor having a gate connected to a gate of the drive transistor, the reference thin film transistor having a reference node coupled to a biasing potential for balancing the current mirror, wherein a first node of the drive thin film transistor corresponding to the reference node is not connected to the biasing potential, thereby preventing a mismatch between the reference thin film transistor and the drive thin film transistor over time; and a capacitor for storing a program voltage independent of a transistor threshold voltage, the program voltage settling on the capacitor while the reference current is conveyed through the reference thin film transistor, the capacitor having a terminal coupled to both the gate of the drive thin film transistor and the gate of the reference thin film transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 16)
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14. A pixel drive circuit for use in a display, the pixel drive circuit comprising:
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switching circuitry for providing a reference current input; a current mirror for providing a drive current to a light emitting device based on the reference current, the current mirror including; a drive thin film transistor for conveying the drive current through the light emitting device, the drive thin film transistor being connected in series with the light emitting device via one of a drain terminal or source terminal of the drive thin film transistor; a reference thin film transistor for receiving the reference current, the reference thin film transistor having a gate connected to a gate of the drive transistor, the reference thin film transistor having a node coupled to a biasing potential via one of a source terminal or a drain terminal of the reference thin film transistor, thereby preventing a mismatch between the reference thin film transistor and the drive thin film transistor over time, wherein one of a source terminal or a drain terminal of the drive thin film transistor corresponding to the one of the source terminal or the drain terminal of the reference thin film transistor is not connected to the biasing potential; and a capacitor for storing a program voltage independent of a transistor threshold voltage, the program voltage settling on the capacitor while the reference current is conveyed through the reference thin film transistor, the capacitor having a terminal coupled to both the gate of the drive thin film transistor and the gate of the reference thin film transistor. - View Dependent Claims (15, 17, 18)
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Specification