VERITAS : multichannel ASIC for pnCCD and DEPFET matrix readout

This thesis work concerns the development of ASICs for X-ray imaging systems, which have to be able to readout and process signals coming from two different sensor types used for different applications: pnCCD and DEPFET. The first project, VERITAS 1.0, has been designed and tested: it consists of a system based on a single-ended readout channel, whose topology is taken from the already implemented ASTEROID channel. The main modifications regards the preamplifier, which has been adapted in order to be able to work with positive and negative gains, which can vary of a factor twenty, and the trapezoidal filter, whose noise contribution has been partially reduced. The 128 channel system has been implemented and tested: linearity, speed and noise performance show good agreement with the simulated ones. Since the filter stage is determinant for the system noise performance, its noise has been thoroughly studied, considering three different methods: the first one relies on a Spectre cadence feature; in the second one the noise has been calculated first evaluating the weighting functions of the main noise sources have been calculated; in the third one a time-domain approximated analysis is performed, considering separately the different filter configurations and its transitions from one configuration to the others. The minimum channel noise is due to the preamplifier stage: its noise has been analytically calculated for the peculiar closed-loop configuration, and its equivalent noise generators have been extracted. The last chapter of the thesis deals with VERITAS 2.0, a new ASIC project based on a fully-differential readout channel; the new topology allows to overcome the main limitations of the previous one, to improve the system dynamic range and to implement a new filter topology with improved noise performance.