An Innovative Analog Circuit to Retrieve Energy Information From Signals of Deeply Saturated Preamplifiers Connected to Semiconductor Detectors

In nuclear spectroscopy, by definition, a distorted signal from a saturated preamplifier cannot contain the correct energy information, being this one directly related to the signal amplitude. In this work, we propose an innovative technique to exploit the charge-conservation principle to extract high-resolution energy information from a deeply saturated charge-sensitive preamplifier (CSP) connected to semiconductor detectors. The previously described "fast-reset" technique enables to reconstruct the energy information from a saturated preamplifier collecting the charge on the input node with a current generator and performing a time-over-threshold (ToT) measurement. However, it requires offline postprocessing of the acquired data. The proposed circuit, instead, requires no postprocessing, thanks to a peculiar time-to-amplitude converter (TAC) that integrates a baseline rejection circuit. In this way, an extension of the preamplifier spectroscopic energy range of a factor 20 or more is possible, with the generation of a signal whose shape is optimized for direct acquisition with a pulse-height analyzer and no additional filtering.