Prototype implementation of a CMOS current mode readout ASIC for X-ray imaging applications

Linear arrays of direct photon conversion (CdTe, GaAs, HgI) sensors are currently under evaluation as detecting elements for X-ray imaging systems. A front-end chain has been designed in CMOS technology with the aim to readout signals produced by these sensors. The current mode architecture was adopted to provide fast signal processing. A polarity select circuit is also included in order to provide the ASIC with the ability to process signals produced from both types of charge carriers (electrons or holes). The dynamic range of the readout chain spans energies from 30keV to 250keV and the operation is optimized for a 2pF total input capacitance. A prototype multichannel ASIC has been fabricated in a 0.6μm CMOS technology including both the analog readout chain and simple digital functionality.