Application Of LTPS TFTs’ Current Model In The Pixel Circuits Of AMOLED

A comprehensive study of LTPS TFTs’ current model will be presented. Current model has been optimized based on previous work. Paying attention to the output characteristic of subthreshold region, a physical-based analytical expression for VDsat_sub of LTPS TFTs is derived. Interpolation functions are introduced to get a unified model which combines current in all region.An analysis on the typical 2T1 C pixel circuit for AMOLED displays based on LTPS TFTs’ on-current model will be presented. We focus on the charging time for the storage capacitor and driving current for the OLED. The parasitic capacitance and degradation of TFT caused nonuniform pixel brightness and poor grayscale accuracy. Variation of driving current is estimated. The analysis based on the analytical poly-Si models is more accurate than the conventional one based on the MOSFET model, and more explicit and flexible than by using a circuit simulator. What’s more, by this method we can determine whether the LTPS TFT device can meet the driving demand.We will analyze pixel circuits based on the unified model through simulation software.Firstly, We use Verilog-A language to accurately describe the relationship of LTPS TFTs’ current and voltage, and then use Hspice which is compatible with Verilog-A to automatically analyze one pixel circuit drived by voltage and one circuit drived by current.The unified model can be applied to actual production.