Monolithic pixel sensors integrate the sensor matrix and readout in the same silicon die, and therefore present several advantages over the more largely used hybrid detectors in high-energy physics. In this paper, a low-power, radiation-hard frontend circuit for monolithic pixel sensors, designed to meet the requirements of low noise and low pixel-to-pixel variability, the key features to achieve high detection efficiencies, is presented. The sensor features a small collection electrode to achieve a small capacitance (< 5 fF) and allows full CMOS in-pixel circuitry. The circuit is implemented in the 180 nm CMOS imaging technology from the TowerJazz foundry and integrated in the MALTA2 chip, which is part of a development that targets the specifications of the outer pixel layer of the ATLAS Inner Tracker upgrade at the LHC. One of the main challenges for monolithic sensors is a radiation hardness up to 1015 1 MeV neq/cm2 Non-Ionizing Energy Loss (NIEL) and 80 Mrad Total Ionizing Dose (TID) required for this application. Radiation source and charge injection tests up to 3 ° 1015 1 MeV neq/cm2 and 100 Mrad were performed on the MALTA2 sensor and front-end circuit, which still show good performance even after these levels of irradiation, promising for even more demanding applications such as the future experiments at the HL-LHC.