Semiconductor device and driving method thereof

摘要

Brightness irregularities that develop in a light emitting device due to is persion among pixels in the threshold values of TFTs used for supplying electric current to light emitting devices become obstacles to improved image quality of the light emitting device. As an image signal input to a pixel from a source signal line, a desired electric potential is applied to a gate electrode of a TFT for supplying electric current to an EL device, through a TFT having its gate and drain connected to each other. A voltage equal to the TFT threshold value is produced between the source and the drain of the TFT 105. An electric potential in which the image signal is offset by the amount of the threshold value is therefore applied to the gate electrode of the TFT. Further, TFTs are disposed in close proximity to each other within the pixel, so that dispersions in the TFT characteristics do not easily develop. A desired drain current can thus be supplied to the EL device even if there is dispersion in the threshold values of the TFTs among pixels, because this is offset by the threshold value of the TFT.

主权项

1. A display device comprising:
a pixel comprising:
an electroluminescent device;a first transistor;a second transistor;a third transistor;a fourth transistor;a fifth transistor; anda capacitor, wherein one of a source and a drain of the first transistor is directly connected to one of a source and a drain of the second transistor, wherein the one of the source and the drain of the first transistor is directly connected to one of a source and a drain of the third transistor, wherein a gate of the first transistor is directly connected to the other of the source and the drain of the second transistor, wherein one of a source and a drain of the fourth transistor is directly connected to the other of the source and the drain of the first transistor, wherein the other of the source and the drain of the fourth transistor is directly connected to a first line, wherein one of a source and a drain of the fifth transistor is directly connected to the other of the source and the drain of the first transistor, wherein the other of the source and the drain of the fifth transistor is directly connected to a second line, wherein the other of the source and the drain of the third transistor is directly connected to the electroluminescent device, wherein a first electrode of the capacitor is directly connected to the gate of the first transistor, wherein a second electrode of the capacitor is directly connected to the first line, wherein a gate of the second transistor is directly connected to a third line, wherein a gate of the fifth transistor is directly connected to the third line, and wherein a gate of the fourth transistor is directly connected to a fourth line.