An optical feedback compensation circuit with a-Si:H thin-film transistors for active matrix organic light emitting diodes

We propose a novel compensation pixel circuit for active matrix organic light emitting diode (AMOLED) display using thin-film transistor (TFT) optical feedback circuit consisting of four switching TFTs, one driving TFT, one photo-sensor and one capacitor. The optical feedback pixel is operated with two gate signals and one scan signal. An integrated scan driver is used to make the scan signal to switch the photo-sensor. Therefore, the AMOLED consisting of the optical feedback pixel circuit and the scan driver can be operated with LCD drivers. By circuit simulation using a Smart Spice, it is found that the proposed circuit can be successfully operated. The gate voltage of driving TFT is automatically discharged and can be compensated for the variation of Vth of driving TFT and degradation of OLED.