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This paper proposes a new pixel circuit using low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of $V_{\mathrm {TH}}$ variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased $T_{\mathrm {COMP}}$ of 33.3 $\mu \text{s}$ results in higher contrast ratio and lower required data voltages than those at $T_{\mathrm {COMP}}$ values of 4.3 and 2.2 $\mu \text{s}$. Red, green, and blue images displayed by the fabricated panel with a $T_{\mathrm {COMP}}$ of 33.3 $\mu \text{s}$ with a 255 gray level are all much more uniform than with $T_{\mathrm {COMPS}}$ of 4.3 and 2.2 $\mu \text{s}$. White images with a $T_{\mathrm {COMP}}$ of 33.3 $\mu \text{s}$ for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with $T_{\mathrm {COMP}}$ values of 4.3 and 2.2 $\mu \text{s}$ are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays. [ABSTRACT FROM AUTHOR]

This brief suppresses threshold voltage (${V}_{\text {TH}}$) variations in low-temperature polycrystalline-silicon thin-film transistors (LTPS TFTs) with a new current scaling ratio modulation method for the application of active-matrix organic light-emitting diode displays. With a newly proposed 3T2C LTPS TFT-based pixel circuit, high-current scaling ratios at low gray levels and low ratios at high gray levels are achieved. Thus, the programming time at low gray levels can be reduced, and the driving currents of the OLED are efficiently generated over the entire data range without consuming extra power for the current source. The driving currents are also independent of the threshold voltage of the driving TFT and the power line voltage, guaranteeing the uniformity of the current. Simulation results demonstrate that the relative current error rates are below 3.7% as the threshold voltage varies ±0.5 V and below 5.3% as the threshold voltage varies ±0.5 V and the power line voltage drops by 1 V; the programming time can be as short as only $12~\mu \text{s}$. [ABSTRACT FROM AUTHOR]

This work proposes a new pixel structure based on amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs) and a parallel addressing scheme for high-resolution active-matrix organic light-emitting diode (AMOLED) displays. The proposed circuit compensates for the nonuniformity of luminance that is caused by shifts in the threshold voltage (${{V}}_{{\rm{TH}}}$) and mobility of driving TFTs. Measurement results verify that the parallel addressing scheme successfully extends the compensation time and accurately detects the ${{V}}_{{\rm{TH}}}$ of the driving TFT. Moreover, the proposed circuit reduces the variations of OLED luminance from more than 83% to less than 13% when the ${{V}}_{{\rm{TH}}}$ and mobility of driving TFT shifts by 1 V and 30%, respectively, and the ${{V}}_{{\rm{TH}}}$ of OLED varies from 0 to 0.9 V. [ABSTRACT FROM PUBLISHER]

This letter presents a new pixel circuit reaching simultaneous compensation for a threshold voltage ( $V_{{\rm{TH}}}$) shift of normally-off and normally- on a-IGZO TFTs, as well as luminance drop of an OLED device for ultrahigh-definition active-matrix organic light-emitting diode displays. Simulation results demonstrate the successful detection of a 1 V shift of threshold voltage despite normally-off and normally-on characteristics by the novel source-follower structure. Furthermore, the interdependence between luminance and threshold voltage shift of the OLED device is measured. Based on the simulations using the measured interdependence, the luminance drop caused by OLED aging is suppressed below 5% at different data voltages. [ABSTRACT FROM PUBLISHER]

This paper presents a simple pixel structure that uses the voltage-programmed method to compensate for the electrical characteristic variations in low-temperature polycrystalline-silicon thin-film transistors and the current-resistance ( \(I\) – \(R\) ) voltage drop in the power line for active-matrix organic light-emitting diode displays. Based on the experimental results, the functionality of the pixel circuit can be operated correctly during each operation phase. Moreover, the pixel current exhibits high uniformity against the threshold voltage and mobility variations in the driving TFT. [ABSTRACT FROM AUTHOR]

This work presents a new external driving scheme that uses the current feedback method with a 3T1C pixel circuit. The proposed circuit provides a stable OLED driving current by compensating for the threshold voltage shift of amorphous-silicon thin-film transistors (a-Si TFTs). For fabricated a-Si TFTs and the 0.35 \mum CMOS process associated with the proposed driving scheme, measurements reveal that the normalized OLED current degradation is less than 5% after 60 hours of operation at 60 ^\circC. Moreover, for a data line load of 1.69 K\Omega/110 pF, the relative error rates between data currents and OLED currents are less than 4% within a settling time of 19 \mu\s. [ABSTRACT FROM PUBLISHER]