Study of PMOS Front-End Solution with Signal Compression for XFEL MiniSDD X-Ray Detectors

In this work we present the study and the experimental results on two different front-end stages for the MiniSDD pixel sensors of the DSSC detector for photon science applications at the European XFEL GmbH in Hamburg. The detector must be able to cope with an image frame rate up to 4.5 MHz and must achieve a dynamic range up to 104 photons/pixel/pulse with a photon energy of 1 keV. In order to achieve this high dynamic range and single photon sensitivity at the same time, the front-end must provide a non-linear amplification. The non-linear response is obtained with a simple circuit that pushes the input PMOSFET into triode region as the input signal increases. Since the readout ASIC has more than 4000 channels operating in parallel, particular care was devoted to the homogeneity and the robustness of the implemented solution, especially with respect to power supply rejection ratio and the cross talk among channels.