Display device
First Claim
1. An active matrix EL display device comprising:
- a plurality of pixels each having a thin film transistor connected to an EL element;
a constant current generator;
a monitoring EL element for monitoring a change in amount of current flowing into the EL element of a pixel, wherein the monitoring EL element has at least a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; and
a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal,wherein the EL element of a pixel is electrically connected to the output terminal of the buffer amplifier, andwherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element.
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Accused Products
Abstract
The image quality of a display device using a bottom gate TFT is improved. In particular, fluctuation in luminance is controlled and the frequency characteristic of a driver circuit is compensated by suppressing a change in amount of current flowing through an EL element which is caused by a change in surrounding temperature while the device is in use. A monitoring EL element is provided in addition to a pixel portion EL element. The monitoring EL element constitutes a temperature compensation circuit together with a buffer amplifier and the like. A current is supplied to the pixel portion EL element through the temperature compensation circuit. This makes it possible to keep the amount of current flowing through the pixel portion EL element constant against a change in temperature, and to control the fluctuation in luminance. An input signal is subjected to time base expansion to perform sampling with accuracy.
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Citations
29 Claims
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1. An active matrix EL display device comprising:
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a plurality of pixels each having a thin film transistor connected to an EL element; a constant current generator; a monitoring EL element for monitoring a change in amount of current flowing into the EL element of a pixel, wherein the monitoring EL element has at least a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; and a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal, wherein the EL element of a pixel is electrically connected to the output terminal of the buffer amplifier, and wherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element. - View Dependent Claims (2, 3, 4, 5, 26)
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6. An active matrix EL display device comprising:
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a constant current generator; a monitoring EL element having at least a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal; a plurality of pixels in a pixel portion, wherein each of the plurality of pixels has a thin film transistor electrically connected to an EL element; and a power supply line for supplying a voltage to the plurality of pixels, wherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element, wherein the EL element of a pixel is electrically connected to the output terminal of the buffer amplifier via the power supply line, and wherein the monitoring EL element is formed separately from the pixel portion and monitors a change in amount of current flowing into the EL element of a pixel. - View Dependent Claims (7, 8, 9, 10, 27)
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11. An active matrix EL display device comprising:
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a plurality of pixels each having a thin film transistor electrically connected to an EL element; a constant current generator; a monitoring EL element for monitoring a change in amount of current flowing into the EL element of a pixel, wherein the monitoring EL element has at least a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal; and an adder circuit having an input terminal and an output terminal, wherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element, wherein the input terminal of the adder circuit is electrically connected to the output terminal of the buffer amplifier, and wherein the output terminal of the adder circuit is electrically connected to the EL element of a pixel. - View Dependent Claims (12, 13, 14, 15, 28)
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16. An active matrix EL display device comprising:
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a plurality of pixels each having a thin film transistor electrically connected to an EL element; a constant current generator; a monitoring EL element having a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal; and an adder circuit having an input terminal and an output terminal, wherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element, wherein the input terminal of the adder circuit is electrically connected to the output terminal of the buffer amplifier, wherein the output terminal of the adder circuit is electrically connected to the EL element of a pixel, and wherein the adder circuit comprises a non-inversion amplifier circuit. - View Dependent Claims (17, 18, 19, 20)
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21. An active matrix EL display device comprising:
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a constant current generator; a monitoring EL element having a first electrode, a second electrode and an EL layer between the first electrode and the second electrode; a buffer amplifier having a non-inversed input terminal, an inversed input terminal and an output terminal; a power supply line for supplying a voltage to the plurality of pixels, an adder circuit having an input terminal and an output terminal; and a plurality of pixels in a pixel portion, wherein each of the plurality of pixels has a thin film transistor electrically connected to an EL element, wherein the non-inversed input terminal of the buffer amplifier is electrically connected to the first electrode of the monitoring EL element, wherein the input terminal of the adder circuit is electrically connected to the output terminal of the buffer amplifier, wherein the EL element of a pixel is electrically connected to the output terminal of the adder circuit via the power supply line, and wherein the monitoring EL element is formed separately from the pixel portion and monitors a change in amount of current flowing into the EL element of a pixel. - View Dependent Claims (22, 23, 24, 25, 29)
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Specification