A CMOS Readout Circuit with Low Detection Limit and High Linearity for Perovskite-based Direct X-ray Detector

A CMOS readout circuit with low detection limit and high linearity for perovskite-based direct X-ray detector is proposed in this paper. We model the input signal of perovskite as a current source and the readout circuit includes a 64 × 64 four-transistor active pixel sensor (4T APS) pixel array and an amplification circuit with 1.2× voltage magnification. The pixel size is 20μm×20μm and a 15.5fF MIM capacitor is employed to convert the input current into voltage during the integration time. Correlated double sample (CDS) structure is designed to decrease the random noise. The circuit is designed with SMIC 180nm Mixed Signal process. The current range of perovskite is 0-2.25pA and the corresponding output voltage is -442.5mV-864.7mV within 10ms typical integration time. The linearity of signal exceeds 99%.