Driving method of light emitting device and light emitting device

Abstract

A driving method of a light emitting device, in which when an N-type driving TFT is connected to an anode of a light emitting element or a P-type driving TFT is connected to a cathode thereof, the driving TFT operates in a saturation region and an image can be displayed with a desired gray scale level depending on a video signal. In addition, a light emitting device adopting the driving method is provided. According to the invention, when a potential having image data is supplied to a gate of a driving TFT depending on a video signal, a reverse bias voltage is applied to the driving TFT and a light emitting element which are connected in series with each other. Meanwhile, when a pixel displays an image depending on the video signal, a forward bias voltage is applied to the driving TFT and the light emitting element.

1 . (canceled) 
     
     
         2 . A light emitting device comprising:
 a scan line;   a first signal line;   a second signal line;   a power supply line;   a first transistor;   a second transistor;   a third transistor;   a fourth transistor;   a first capacitor;   a second capacitor;   a first light emitting element; and   a second light emitting element,   wherein a gate of the first transistor is connected to the scan line,   wherein one of a source and a drain of the first transistor is connected to the first signal line,   wherein the other of the source and the drain of the first transistor is directly connected to a gate of the second transistor,   wherein one of a source and a drain of the second transistor is connected to the first light emitting element,   wherein the other of the source and the drain of the second transistor is directly connected to the power supply line,   wherein a first electrode of the first capacitor is connected to the gate of the second transistor,   wherein a second electrode of the first capacitor is connected to the one of the source and the drain of the second transistor,   wherein a gate of the third transistor is connected to the scan line,   wherein one of a source and a drain of the third transistor is connected to the second signal line,   wherein the other of the source and the drain of the third transistor is directly connected to a gate of the fourth transistor,   wherein one of a source and a drain of the fourth transistor is connected to the second light emitting element,   wherein the other of the source and the drain of the fourth transistor is directly connected to the power supply line,   wherein a first electrode of the second capacitor is connected to the gate of the fourth transistor, and   wherein a second electrode of the second capacitor is connected to the one of the source and the drain of the fourth transistor.   
     
     
         3 . The light emitting device according to  claim 2 , wherein the power supply line is supplied with a pulse signal. 
     
     
         4 . The light emitting device according to  claim 2 , wherein the power supply line is functionally connected to an inverter. 
     
     
         5 . An electronic apparatus comprising the light emitting device according to  claim 2  and a housing. 
     
     
         6 . A light emitting device comprising:
 a first line;   a second line;   a third line;   a fourth line;   a first transistor;   a second transistor;   a third transistor;   a fourth transistor;   a first capacitor;   a second capacitor;   a first light emitting element; and   a second light emitting element,   wherein a gate of the first transistor is connected to the first line,   wherein one of a source and a drain of the first transistor is connected to the second line,   wherein the other of the source and the drain of the first transistor is directly connected to a gate of the second transistor,   wherein one of a source and a drain of the second transistor is connected to the first light emitting element,   wherein the other of the source and the drain of the second transistor is directly connected to the fourth line,   wherein a first electrode of the first capacitor is connected to the gate of the second transistor,   wherein a second electrode of the first capacitor is connected to the one of the source and the drain of the second transistor,   wherein a gate of the third transistor is connected to the first line,   wherein one of a source and a drain of the third transistor is connected to the third line,   wherein the other of the source and the drain of the third transistor is directly connected to a gate of the fourth transistor,   wherein one of a source and a drain of the fourth transistor is connected to the second light emitting element,   wherein the other of the source and the drain of the fourth transistor is directly connected to the fourth line,   wherein a first electrode of the second capacitor is connected to the gate of the fourth transistor, and   wherein a second electrode of the second capacitor is connected to the one of the source and the drain of the fourth transistor.   
     
     
         7 . The light emitting device according to  claim 6 , wherein the fourth line is supplied with a pulse signal. 
     
     
         8 . The light emitting device according to  claim 6 , wherein the fourth line is functionally connected to an inverter. 
     
     
         9 . An electronic apparatus comprising the light emitting device according to  claim 6  and a housing. 
     
     
         10 . A light emitting device comprising:
 a first line;   a second line;   a third line;   a fourth line;   a fifth line;   a sixth line;   a first transistor;   a second transistor;   a third transistor;   a fourth transistor;   a fifth transistor;   a sixth transistor;   a first capacitor;   a second capacitor;   a third capacitor;   a first light emitting element;   a second light emitting element; and   a third light emitting element,   wherein a gate of the first transistor is connected to the first line,   wherein one of a source and a drain of the first transistor is connected to the second line,   wherein the other of the source and the drain of the first transistor is directly connected to a gate of the second transistor,   wherein one of a source and a drain of the second transistor is connected to the first light emitting element,   wherein the other of the source and the drain of the second transistor is directly connected to the fourth line,   wherein a first electrode of the first capacitor is connected to the gate of the second transistor,   wherein a second electrode of the first capacitor is connected to the one of the source and the drain of the second transistor,   wherein a gate of the third transistor is connected to the first line,   wherein one of a source and a drain of the third transistor is connected to the third line,   wherein the other of the source and the drain of the third transistor is directly connected to a gate of the fourth transistor,   wherein one of a source and a drain of the fourth transistor is connected to the second light emitting element,   wherein the other of the source and the drain of the fourth transistor is directly connected to the fourth line,   wherein a first electrode of the second capacitor is connected to the gate of the fourth transistor,   wherein a second electrode of the second capacitor is connected to the one of the source and the drain of the fourth transistor,   wherein a gate of the fifth transistor is connected to the fifth line,   wherein one of a source and a drain of the fifth transistor is connected to the second line,   wherein the other of the source and the drain of the fifth transistor is directly connected to a gate of the sixth transistor,   wherein one of a source and a drain of the sixth transistor is connected to the third light emitting element,   wherein the other of the source and the drain of the sixth transistor is directly connected to the sixth line,   wherein a first electrode of the third capacitor is connected to the gate of the sixth transistor, and   wherein a second electrode of the third capacitor is connected to the one of the source and the drain of the sixth transistor.   
     
     
         11 . The light emitting device according to  claim 10 , wherein the fourth line is not directly connected to the sixth line. 
     
     
         12 . The light emitting device according to  claim 10 ,
 wherein the fourth line is supplied with a first pulse signal, and   wherein the sixth line is supplied with a second pulse signal.   
     
     
         13 . The light emitting device according to  claim 10 , wherein the fourth line is functionally connected to an inverter. 
     
     
         14 . An electronic apparatus comprising the light emitting device according to  claim 10  and a housing.