In this paper, we propose a pixel circuit immune to the electrical characteristic variation of organic light-emitting diodes (OLEDs) for organic light-emitting diode-on-silicon (OLEDoS) microdisplays with a 0.4 inch video graphics array (VGA) resolution and a 6-bit gray scale. The proposed pixel circuit is implemented using five p-channel metal oxide semiconductor field-effect transistors (MOSFETs) and one storage capacitor. The proposed pixel circuit has a source follower with a diode-connected transistor as an active load for improving the immunity against the electrical characteristic variation of OLEDs. The deviation in the measured emission current ranges from -0.165 to 0.212 least significant bit (LSB) among 11 samples while the anode voltage of OLED is 0 V. Also, the deviation in the measured emission current ranges from -0.262 to 0.272 LSB in pixel samples, while the anode voltage of OLED varies from 0 to 2.5 V owing to the electrical characteristic variation of OLEDs.

An ambient light sensing function, which is one of several value-added functions in system-on-panel (SoP), can contribute to low power consumption and improve visibility by auto brightness control. However, it is very challenging to read the photoleakage current of p-intrinsic-n (PIN) diode directly, which is generally used as a photodetector in SoP. Therefore, we propose an ambient light sensing circuit using low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) and the PIN diode, which can output analog voltage converted from the photo-leakage current of the PIN diode. Through the measurement of the proposed circuits under ambient light variations from 0 to 2000 lx, we confirmed that the proposed ambient light sensing circuits can perform sensing and readout operations accurately. The dynamic range of the proposed circuit is 35 dB and the maximum variation of the output voltage among eight samples is AE45 mV.

We study the relaxation properties of the voter model with i.i.d. random bias. We prove under mild conditions that the disorder-averaged relaxation of this biased random voter model is faster than a stretched exponential with exponent d/(d + α), where 0 < α 2 depends on the transition rates of the non-biased voter model. Under an additional assumption, we show that the above upper bound is optimal. The main ingredient of our proof is a result of Donsker and Varadhan. § Postdoctoraal onderzoeker FWO. Bursaal IWT. 0305-4470/99/447653+12$30.00

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Photo sensing circuits using low-temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) and thin film photo diode such as p-intrinsic-n (p-i-n) diode and p-intrinsic-metal (pi-m) diode have been studied for several smart functions such as optical touch screen, ambient light sensor, and image scanner. In this paper, aforementioned photo sensing circuits for smart functional displays are reviewed. Also, the driving method for compensation of the temperature characteristic of photo diode is presented.