Two-TFT pixel driving circuit was simulated and analyzed for Active Matrix OLED using AIM Spice in this paper.From the simulation results

the influences of the driving transistor T

2

W/L

ratios on the OLED current were shown.For a typical OLED emission efficiency

and a known pixel area

a current level is needed to achieve the pixel brightness.By the simulation results

reasonable T

2

W/L

ratios can be obtained.The simulation results also showed that the OLED grayscale could be adjusted by changing the data voltage.On the other hand

the source voltage should be high enough to ensure the T

2

operates the saturation state.Further more

the two-TFT pixel electrode circuit transient characteristic was simulated.The impact of the T

1

W/L

ratios and storage capacitor on output characteristic was discussed.The lower size capacitor will reduce the OLED current during the pixel electrode OFF period.And too large capacitor will deduce a large charge time constant

which impacts on the respond speed and brightness of OLED.The larger T

1

W/L

ratios will also result in the drop of the OLED current during the pixel electrode OFF period.So they need to be carefully selected.From the transient characteristic of the influences of the value of scan pulse voltage on output current

it is clear that the lower scan voltage value will result in the OLED current is not proportional to data voltage.Thus the OLED brightness cannot follow the variation of the data voltage.The increasing of scan voltage value will solve the above problem. Form the temperature characteristic

the two-TFT pixel driving circuit cannot overcome the effect on OLED current because of the shift of threshold of the driving TFT due to the manufacturing variations and the circuit aging. The simulation results indicate that if the parameters are chosen properly

driving circuit can ensure the OLED brightness requirement and the constant output current in a frame time

and the grayscale can be adjusted by changing data voltage.Simulation results showed the various parameter effect on the circuit performance.On this basis

we obtain the more reasonable parameter value about two-TFT pixel electrode circuit.Those analyses supply base for driving circuit design

parameter choice

performance analyses and layout design for Active Matrix OLED.