Semiconductor Energy Laboratory Co., Ltd.

Shou Nagao

Munehiro Azami

Yoshifumi Tanada

Mitsuaki Osame

Yutaka Shionoiri

Jun Koyama

Yukio Tanaka

Naoko Yano

Shunpei Yamazaki

Hiroyuki Miyake

Hideto Ohnuma

Masaaki Hiroki

Tomoyuki Iwabuchi

Hitomi Ushitani

Hajime Kimura

Hisashi Ohtani

Aya Anzai

Yu Yamazaki

Keisuke Miyagawa

A pulse is inputted to TFTsandso that the TFTs would turn ON and then potential of a node a rises. When the potential of the node &#x3b1; reaches (VDD&#x2212;VthN), the node &#x3b1; became in a floating state. Accordingly, a TFTthen turns ON, and potential of an output node rises as a clock signal reaches the level H. On the other hand, potential of a gate electrode of the TFTfurther rises due to an operation of capacitanceas the potential of the output node rises, so that the potential of the output node would be higher than (VDD+VthN). Thus, the potential of the output node rises to VDD without voltage drop caused by a threshold of the TFT

Pulse output circuit, shift register and display device

A pulse is inputted to TFTsandso that the TFTs would turn ON and then potential of a node &#x3b1; rises. When the potential of the node &#x3b1; reaches (VDD&#x2212;VthN), the node &#x3b1; became in a floating state. Accordingly, a TFTthen turns ON, and potential of an output node rises as a clock signal reaches the level H. On the other hand, potential of a gate electrode of the TFTfurther rises due to an operation of capacitanceas the potential of the output node rises, so that the potential of the output node would be higher than (VDD+VthN). Thus, the potential of the output node rises to VDD without voltage drop caused by a threshold of the TFT

A circuit is provided which is constituted by TFTs of one conductivity type, and which is capable of outputting signals of a normal amplitude. When an input clock signal CKbecomes a high level, each of TFTs () is turned on to settle at a low level the potential at a signal output section (Out). A pulse is then input to a signal input section (In) and becomes high level. The gate potential of TFT () is increased to (VDD&#x2212;V thN) and the gate is floated. TFT () is thus turned on. Then CKbecomes low level and each of TFTs () is turned off. Simultaneously, CKbecomes high level and the potential at the signal output section is increased. Simultaneously, the potential at the gate of TFT () is increased to a level equal to or higher than (VDD+V thN) by the function of capacitor (), so that the high level appearing at the signal output section (Out) becomes equal to VDD. When SP becomes low level; CKbecomes low level; and CKbecomes high level, the potential at the signal output section (Out) becomes low level again.

Pulse output circuit, shift register, and display device

There is provided a semiconductor device in which fabrication steps can be reduced by constructing a circuit using only TFTs of one conductivity type and in which a voltage amplitude of an output signal can be normally obtained. A capacitance () is provided between a gate and a source of a TFT () connected to an output node, and a circuit formed of TFTs () and () has a function to bring a node &#x3b1; into a floating state. When the node &#x3b1; is in the floating state, a potential of the node &#x3b1; is caused higher than VDD by using gate-source capacitance coupling of the TFT () through the capacitance (), thus an output signal having an amplitude of VDD&#x2212;GND can be normally obtained without causing amplitude attenuation due to the threshold value of the TFT.

Semiconductor device

A display device comprises a display panel composed of a pixel portion in which a plurality of TFTs are arranged in matrix, a source driver, and a gate driver, an image signal processing circuit for processing an image signal input from an external, and a control circuit for controlling the display panel and the image signal processing circuit. The image signal processing circuit corrects the image signal on the basis of a correction table. By feeding the display panel with the corrected image signal, the display device can provide a good quality image.

Display device and method for operating the same

A pulse is input to first and second TFTs to turn ON the first and second TFTs so that the potential of a node a rises. When the potential of the node a reaches (VDD&#x2212;VthN), the node &#x3b1; enters a floating state. Accordingly, a third TFT then turns ON, and potential of an output node rises as a clock signal reaches the level H. On the other hand, potential of a gate electrode of the third TFT further rises due to an operation of capacitance as the potential of the output node rises, so that the potential of the output node would be higher than (VDD+VthN). Thus, the potential of the output node rises to VDD without voltage drop caused by a threshold of the third TFT.

There is provided a semiconductor device in which fabrication steps can be reduced by constructing a circuit using only TFTs of one conductivity type and in which a voltage amplitude of an output signal can be normally obtained. A capacitance () is provided between a gate and a source of a TFT () connected to an output node, and a circuit formed of TFTs () and () has a function to bring a node &#x3b1; into a floating state. When the node &#x3b1; is in the floating state, a potential of the node &#x3b1; is caused higher than VDD by using gate-source capacitance coupling of the TFT () through the capacitance (), thus an output signal having an amplitude of VDD-GND can be normally obtained without causing amplitude attenuation due to the threshold value of the TFT.

A drive circuit of a display device, which comprise only single conductive TFTs and in which amplitude of an output signal is normal, is provided. A pulse is inputted to TFTsandso that the TFTs would turn ON and then potential of a node &#xe1; rises. When the potential of the node &#xe1; reaches (VDD&#x2212;VthN), the node &#xe1; became in a floating state. Accordingly, a TFTthen turns ON, and potential of an output node rises as a clock signal reaches the level H. On the other hand, potential of a gate electrode of the TFTfurther rises due to an operation of capacitanceas the potential of the output node rises, so that the potential of the output node would be higher than (VDD+VthN). Thus, the potential of the output node rises to VDD without voltage drop caused by a threshold of the TFT. An output at the subsequent stage is then inputted to TFTsandto turn the TFTsandON, while the potential of the node &#xe1; drops down to turn the TFTOFF. A TFTturns ON at the same time so that the potential of the output node would reach the level L.

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Kanagawa, Japan

Shou Nagao