Performance of Analog Pixel Test Structure of monolithic sensors with Operational Amplifier output buffer for ALICE ITS3 upgrade.

A new vertex detector composed of curved ultra-thin monolithic silicon sensors arranged in cylindrical layers is planned to be installed during the LHC LS3 to replace the innermost three layers of the ALICE Inner Tracking System at CERN. This contribution explores the first tests on the Analog Pixel Test Structure with an Operational Amplifier output buffer (APTS OPAMP). The sensor matrix is a $4\times 4$ pixels test structure with analogue output channels and the aim of this technology is to provide an excellent timing performance by exploiting a high-speed operational amplifier buffer. Laboratory tests conducted through the in pixel pulsing circuit had allowed to find the best working point through a detailed study of the circuital parameters and they will be exposed together with the characterization with a $^{55}Fe$ source, demonstrating promising performances in terms of timing and charge collection efficiency. Finally, the results of the beam tests that took place at the Super Proton Synchrotron (SPS) at CERN, which operates at up to $450 {GeV}$, on the Analog Pixel Test Structure of monolithic sensors with OPAMP buffer will be presented.