Implementation of correlated double sampling circuit on glass applied for active pixel sensing array

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 (V-th) 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 V-th variation is eliminated and readout voltage dynamic range is adjusted to fit the operation region of IC at the same time.