| 摘要 |
A light emitting device is provided to secure uniform luminance and to prevent the luminance change of an EL(Electroluminescence) element by controlling the luminance by current instead of voltage. A light emitting device has plural pixels(101) composed of four TFTs(Thin Film Transistors,102,103,104,105), an EL element(106), a source signal line(Si), and a power supply line(Vi). The third and fourth TFTs are connected to each other at gate electrodes. One of a source region and a drain region of the third TFT is connected to the source signal line and the other is coupled to a drain region of the first TFT. One of source and drain regions of the fourth TFT is connected to the drain region of the first TFT and the other is connected to a gate electrode of the first TFT. A source region of the first TFT is connected to the power supply line and a drain region is connected to a source region of the second TFT. A drain region of the second TFT is linked to one of two electrodes of the EL element.
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