利用少數TFT實行元件特性變異補償之主動式光感測電路研究

Abstract

高解析度主動式光感測電路一直備受關注，因為它能放大感測信號，可應用在許多重要領域，如X光面板成像器等。採用玻璃上的薄膜電晶體作為該電路作為放大和開關元件，可實現大面積化，但是電晶體特性會因為製程上的誤差或是長時間的使用產生變異，而造成感測誤差。若為了補償此變異而使電路複雜化，則無法達成高解析度。 在本論文中，我們針對一次讀取和連續讀取的兩種功能性，分別提出了電壓和電流補償模式的各種電路，來補償電晶體特性的變異，並利用模擬來驗證這些電路的補償效果，且比較其優劣。經由這些研究，我們提出了以最少電晶體實現的光感測電路，其具有元件特性變異補償的功能，可達到高解析度感測面板的需求，且可避免因元件截止電壓變動所產生的誤差。

High resolution active light sensing pixel circuits have drawn great attention abidingly because they can amplify the sensing signals. It can be applied in many important domains, such as X-ray flat panel imager. Using thin film transistors on glass substrates as the amplifying and switching devices in pixel circuit, a large area panel is achievable. Nevertheless, the process variation or the degradation in long-term operation device can result in the sensing error. If a complicated circuit is used to compensate the variation, the resolution of the imager cannot be made high. In this thesis, for both the two operation modes of snap-shot and rolling-readout, we propose the voltage-programmed and current- programmed circuits for the device variation compensation, respectively. The simulation is used to verify the compensating performance of these circuits. In addition, their merits and drawbacks are compared. Through the research, we develop the light sensing circuits implemented by the fewest TFTs with device variation compensating function. The circuits can meet the requirement for the high resolution flat panel imager, and minimized the errors resulting from threshold voltage shift.