Large area thin film circuits
AssigneeKoninklijke Philips Electronics N.V.
InventorSteven Charles Deane
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Abstract
A thin film circuit comprises a plurality of thin film transistors, wherein the output response of the circuit is dependent on at least first (36) and second (34, 22) of the transistors. The first thin film transistor (36) is, in use, exposed to a source of illumination (2) and the second thin film transistor (16) is shielded from the source of illumination. The first thin film transistor (36) is operated in use as an analogue switch which provides an analogue output in response to a control input. The illumination of this transistor reduces the effect of dynamic threshold voltage variations, which can be a limitation to circuit performance.
Claims11
A thin film circuit, comprising a plurality of thin film transistors, wherein the output response of the circuit is dependent on at least first and second of the transistors, wherein the first thin film transistor is, in use, exposed to a source of illumination and the second thin film transistor is shielded from the source of illumination, and wherein the first thin film transistor is operated in use as an analogue device which provides an analogue output sensitive to the threshold voltage in response to a control input.
An active matrix display device comprising an array of display pixels, each pixel comprising a thin film circuit, the thin film circuit comprising:
- a current-driven light emitting display element;
- a drive transistor for driving a current through the display element;
- a storage capacitor for storing a voltage to be used for addressing the drive transistor;
- an address transistor for switching a drive voltage to the remainder of the pixel;
- a discharge transistor for discharging the storage capacitor thereby to switch off the drive transistor;
- and
- a light-dependent device for controlling the timing of the operation of the discharge transistor by varying the gate voltage applied to the discharge transistor (36) in dependence on the light output of the display element, wherein the first transistor comprises the discharge transistor and the second transistor comprises the address transistor.
An active matrix liquid crystal display device comprising an array of display pixels and drive circuitry, where the drive circuitry comprises a thin film circuit, the thin film circuit comprising a plurality of thin film transistors, wherein the output response of the circuit is dependent on at least first and second of the transistors, wherein the first thin film transistor is in use exposed to a source of illumination and the second thin film transistor is shielded from the source of illumination, and wherein the first thin film transistor is operated in use as an analogue device which provides an analogue output sensitive to the threshold voltage in response to a control input, and wherein the device further comprises a backlight providing the source of illumination.
A method of controlling a thin film circuit comprising a plurality of thin film transistors, wherein the output response of the circuit is dependent on at least first and second of the transistors, the method comprising:
- exposing the first thin film transistor to a source of illumination;
- shielding the second thin film transistor from the source of illumination;
- and
- operating the first thin film transistor as an analogue device which provides an analogue output sensitive to the threshold voltage in response to a control input.
Dependencies are inferred from the claim text.