Charge preamplifier in a 65 nm CMOS technology for pixel readout in the Grad TID regime

A charge preamplifier has been developed in a 65 nm CMOS technology for processing the signal from the inner pixel layers of the CMS detector, in view of the experiment upgrade for the High Luminosity (HL) LHC. The circuit is part of a readout channel implementing a time-over-threshold method for analog-to digital-conversion of the charge signal. Samples of the circuit have been exposed to high doses of ionizing radiation, up to 8 MGy, from a low energy proton source. The main purpose is to study the radiation-induced degradation of the preamplifier parameters (charge sensitivity, noise, signal shape), in view of its use in the harsh environment of the HL-LHC, where integrated ionizing doses in the range of 1 Grad are expected during the detector lifetime.