With the gradual popularization of Internet of Things (IoT) and automation related technologies as well as the rapid development of biometric technology, the application requirements for image sensors have also increased. The improvement of the accuracy of the sensing results has always been a project that people continue to study and optimize. The characteristic of the thin film transistor (TFT), which is often used in active pixel sensor (APS), is likely been affected by temperature and the error during fabrication process, thereby affecting the sensing accuracy. The threshold voltage (Vth) variation is one of the most influential factors among all non‐ideal effect. Correlated double sampling (CDS) is a commonly used technique in eliminating the characteristic variation. In this paper, we proposed a novel CDS circuit composed of TFTs and capacitors which can be integrated on substrate with simulation and implementation. The advantage of the circuit is that Vth variation is eliminated and readout voltage dynamic range is adjusted to fit the operation region of IC at the same time.
In recent years, promoting the sensing accuracy of the image pixel sensor has become a hot issue. For voltage type active pixel sensor (V‐APS), the readout voltage, as well as the sensing signal, will be affected by the thin film transistors (TFTs) characteristic variation, especially the shift in threshold voltage (Vth). In this paper, we introduce a novel correlated double sampling (CDS) circuit, which can be implemented on glass by only using TFTs and capacitors. Thus, the readout voltage variation due to the threshold voltage shift under same light intensity illumination can be eliminated.
Gap-type amorphous silicon (a-Si) thin-film transistor (TFT) used as photo sensor has been reported in previous literature. However, the noise behavior of gap-type a-Si TFT is not inspected yet. Therefore, we investigate the noise response of the gap-type a-Si TFT under illumination in this paper. We compare the difference between the results of the gap-type and the conventional-type TFTs. In addition, we analyze it including the perspectives of power spectrum, integral power spectrum, Hooge parameter, fluctuate slope. Finally, we explain the reason for its fluctuate slope transition and review the correlation between noise behavior and photo effect mechanism.INDEX TERMS Amorphous silicon, gap-type, thin-film transistors (TFTs), noise.
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