The Research And Design Of Gate Driver Circuit Integrated By Metal Oxide Thin Film Transistors Applied In AMOLED Displays

Thin film transistor(TFT) is the key device in flat panel display. In recent years, metal oxide TFT has gained much attention because of its high performance and low-price fabracation. Active Matrix Organic Light Emitting Diode(AMOLED) has a lot of excellent features, such as self-light emitting, high speed of response, flexiable display. So it is considered to be the most promising display technology with low cost, large size and high resolution in the next generation. Metal oxide TFT applied in AMOLED display is becoming a hot topic. Metal oxide TFTs wih high performance can not only drive the pixel circuit in AMOLED displays, but also be applied in peripheral integrated circuit especially about the integrated gate driver circuit, which can meet the requirement of timing diagram of the complicatied compensation pixel circuit. There are also many advantages about the integrated gate driver circuit, simpler process, lower price, narrower bezel and so on.This article is mainly about the research and design of gate driver circuit integrated by metal oxide TFTs in AMOLED dispays. In the beginning, a specific simulation model is provided for verification of the integrated circuit by fitting the test characteristics of metal oxide TFTs. Then a new highly stable integrated gate driver circuit employing metal oxide TFTs is presented. The simulating verification for the proposed circuit is also given. Moreover, the experiment results show that the proposed circuit with 480 stages can work stably. And the output signal chages little afer 120 hour’s operation, which shows a good reliability. In the end, a 3 inch demonstration panel of 320*480 AMOLED display by metal oxide TFTs process is fabricated to verify the function of the proposed circuit using bi-side driving method. It shows that this highly stable gate driver circuit integrated by metal oxide TFTs has the potential for being applied in AMOLED displays.Another integrated gate driver circuit employing single negative power supply is also proposed. The pull-down TFTs circuit can be turned off completely in the output generation period by the capacity coupling effect when the high level of driving clock sets low. Similarily, the principle of this circuit is analyzed and verified by simulation. Furhtermore, the experiment results show that this circuit can generate output signal successfully with little distortion, which implies that it is potential for AMOLED displays. It gives a new orientation for the research of gate driver circuit integrated by metal oxide TFTs.