Abstract
Recently, for interactive purposes, detecting devices are been developed on the existing TFT-LCD panels. Many of them are based on resistive, capacitive or inductive touch technology. All these solutions require externally added components or one more layer of screen, which add the cost and degrade the optical performance. In our study, we use a novel approach by building an additional TFT photo-diode in the existing LCD display pixel as a detecting element. This diode can be embedded during the panel manufacturing process and incurring no additional cost. After the post-product evaluation, this diode also shows no impediment to the light efficiency. In this way, by using the photo-diode array and by going with a designed detecting circuit, the imaging signal that appears on the panel can then be read out.In this study we investigate a readout circuit that can be used to distinguish the noise that comes from environment and the signal that comes from our remote controlled light-pen on hand. By the circuit we can get the required results of lower power consumption and smaller integrated chip area in comparison with using conventional ADC. In addition to the advantage of low power supply it has high output voltage swing and is suitable for implementation in advanced submicron CMOS technologies. The circuit proposed above is design in a TSMC 0.35um process and verified by HSPICE program.