Threshold voltage shift

1
Introduction

• Threshold voltage shift
• Creation of dangling bond defects
• Charge trapping

2
The role ?Vth play in AMOLED
AM-OLED Driving Circuit

• OLED is a current-driving device.
• In saturation mode of TFT

Vdd
Row
OLED
Data
3
Operation of the Proposed Pixel Circuit
Vcc

• Compensation Period
• Row ? 0V
• Data ? 0V
• AZ ? High

VdataVth
Vdata
High
0V
OLED
Row
-Vth
0V
C1
Vdata
C
0V
A
B
Data
DTFT
T1

• Emission Period
• Row ? High
• Data ? Vdata
• AZ ? Low

T3
T2
AZ
R1
High
Low
Vnegative
4
Operation of the Proposed Pixel Circuit

• When TFT is in saturation mode
• In this case, VGS VdataVth
• IOLED is independent of Vth of TFT.