This paper introduces novel driving methods of the pull-down unit in a gate driver circuit for enhancement- and depletion-mode a-IGZO thin-film transistors (TFTs). The proposed gate driver circuit can achieve uniform output characteristics and effectively reduce the $\text{V}_{\mathrm{ OUT}}$ ripple voltage because the threshold voltage ( $\text{V}_{\mathrm{ TH}}$ ) of the pull-down units is compensated regardless of the a-IGZO TFT operation characteristics (enhancement mode: positive value of $\text{V}_{\mathrm{ TH}}$ , depletion mode: negative value of $\text{V}_{\mathrm{ TH}}$ ). Many groups proposed the $\text{V}_{\mathrm{ TH}}$ compensation method for pull-down TFTs in the gate driver circuit using a diode connection structure. However, the diode connection structure to extract the $\text{V}_{\mathrm{ TH}}$ value cannot be applied in the depletion-mode oxide TFTs because TFT enters the turn-on state even when the $\text{V}_{\mathrm{ GS}}$ value is 0 V. To solve this problem, we adopted the $\text{V}_{\mathrm{ TH}}$ extraction period only once in one frame time. As a result, our circuit can compensate for $\text{V}_{\mathrm{ TH}}$ of the pull-down unit in the enhancement mode and can be normally operated in the depletion mode. Adjunctively, two low signals (VGL1 and VGL2) and QC node were designed to prevent the leakage current path for Q and $\text{V}_{\mathrm{ OUT}}$ nodes. To verify the threshold voltage tolerance for various stress conditions, we demonstrated the reliability of the circuit according to the threshold voltage change of the TFTs. The simulation result shows that all the $\text{V}_{\mathrm{ OUT}}$ waveforms are maintained at +28 V (VGH) under the $\text{V}_{\mathrm{ TH}}$ shift conditions from −7 V to +11 V; further, the rising time and falling time are less than $0.62~{\mu }\text{s}$ and $0.96~{\mu }\text{s}$ , respectively. Based on a 120-Hz ultra-high definition (UHD) graphics ( $3840{\times }2160$ ) display panel, the proposed circuit has uniform $\text{V}_{\mathrm{ OUT}}$ characteristics compared to previous $\text{V}_{\mathrm{ TH}}$ compensation circuit when $\Delta \text{V}_{\mathrm{ TH}}$ changes from −3 V to +11 V. When $\Delta \text{V}_{\mathrm{ TH}}$ changes from −4 V to −7 V, there is also no circuit malfunction, even with slight increase in the falling time and power consumption.

中文翻译：

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增强型和耗尽型氧化物 TFT 栅极驱动器的新型驱动方法

本文介绍了增强型和耗尽型 a-IGZO 薄膜晶体管 (TFT) 栅极驱动电路中下拉单元的新型驱动方法。所提出的栅极驱动电路可以实现均匀的输出特性并有效降低 $\text{V}_{\mathrm{ OUT}}$ 纹波电压因为阈值电压（ $\text{V}_{\mathrm{ TH}}$ ) 的下拉单元得到补偿，而不管 a-IGZO TFT 操作特性如何（增强模式：正值 $\text{V}_{\mathrm{ TH}}$ ，耗尽模式：负值 $\text{V}_{\mathrm{ TH}}$ ）。许多团体提出了 $\text{V}_{\mathrm{ TH}}$ 采用二极管连接结构的栅极驱动电路中下拉TFT的补偿方法。然而，二极管连接结构提取 $\text{V}_{\mathrm{ TH}}$ 值不能应用于耗尽型氧化物 TFT，因为 TFT 进入导通状态，即使在 $\text{V}_{\mathrm{ GS}}$ 值为 0 V。为了解决这个问题，我们采用了 $\text{V}_{\mathrm{ TH}}$ 一帧时间内仅提取一次。因此，我们的电路可以补偿 $\text{V}_{\mathrm{ TH}}$ 下拉单元在增强模式下可以正常工作在耗尽模式下。此外，还设计了两个低信号（VGL1 和 VGL2）和 QC 节点，以防止 Q 和 $\text{V}_{\mathrm{ OUT}}$ 节点。为了验证各种应力条件下的阈值电压容限，我们根据 TFT 的阈值电压变化证明了电路的可靠性。仿真结果表明，所有 $\text{V}_{\mathrm{ OUT}}$ 波形保持在 +28 V (VGH) $\text{V}_{\mathrm{ TH}}$ 将条件从 -7 V 转移到 +11 V；此外，上升时间和下降时间小于 $0.62~{\mu}\text{s}$ 和 $0.96~{\mu}\text{s}$ ， 分别。基于 120 Hz 超高清 (UHD) 图形 ( $3840{\times }2160$ ) 显示面板，建议电路具有统一 $\text{V}_{\mathrm{ OUT}}$ 与以往相比的特点 $\text{V}_{\mathrm{ TH}}$ 补偿电路当 $\Delta \text{V}_{\mathrm{ TH}}$ 从 -3 V 变为 +11 V。当 $\Delta \text{V}_{\mathrm{ TH}}$ 从−4 V 到−7 V，即使下降时间和功耗略有增加，也没有电路故障。