Method of Driving Display Device

Abstract

An active matrix type EL display device is provided, which is capable of suppressing the unevenness of luminance display due to the unevenness of the characteristics of TFTs which constitute pixels, or due to variations in the environmental temperature at which the display device is used. The active matrix type EL display is driven by a time gray scale method, and is capable of keeping the drain current of each of its EL driving TFTs constant by operating each of the EL driving TFTs in a saturation region in an ON state. Accordingly, constant current can be made to flow in each of the EL elements, whereby it is possible to provide an active matrix type EL display device with accurate gray scale display and high image quality.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A display device comprising a pixel, the pixel comprising:
 a first transistor and a second transistor;   a resistor; and   an EL element,   wherein a gate of the first transistor is electrically connected to a gate signal line,   wherein one of a source and a drain of the first transistor is electrically connected to a source signal line,   wherein the other of the source and the drain of the first transistor is electrically connected to a gate of the second transistor,   wherein one of a source and a drain of the second transistor is electrically connected to the EL element,   wherein the other of the source and the drain of the second transistor is electrically connected to a line,   wherein the resistor is electrically connected to the second transistor in series between the EL element and the line, and   wherein a ratio of a gate width of the second transistor to a gate length of the second transistor is less than 1.   
     
     
         3 . The display device according to  claim 2 , wherein the line is a power supply line. 
     
     
         4 . The display device according to  claim 2 , wherein each of the first transistor and the second transistor is an n-channel TFT. 
     
     
         5 . The display device according to  claim 2 , wherein each of the first transistor and the second transistor comprises a crystalline semiconductor film. 
     
     
         6 . The display device according to  claim 2 , wherein the second transistor is operated in a saturation region when the EL element is in an emitting state. 
     
     
         7 . The display device according to  claim 2 , wherein the resistor is positioned between the line and the second transistor. 
     
     
         8 . The display device according to  claim 2 , wherein the EL element comprises a red color light-emitting layer. 
     
     
         9 . An electronic device comprising the display device according to  claim 2 .