  Monolithic active pixel sensors produced in High Voltage CMOS (HV-CMOS)
technology are being considered for High Energy Physics applications due to the
ease of production and the reduced costs. Such technology is especially
appealing when large areas to be covered and material budget are concerned.
This is the case of the outermost pixel layers of the future ATLAS tracking
detector for the HL-LHC. For experiments at hadron colliders, radiation
hardness is a key requirement which is not fulfilled by standard CMOS sensor
designs that collect charge by diffusion. This issue has been addressed by
depleted active pixel sensors in which electronics are embedded into a large
deep implantation ensuring uniform charge collection by drift. Very first small
prototypes of hybrid depleted active pixel sensors have already shown a
radiation hardness compatible with the ATLAS requirements. Nevertheless, to
compete with the present hybrid solutions a further reduction in costs
achievable by a fully monolithic design is desirable. The H35DEMO is a large
electrode full reticle demonstrator chip produced in AMS 350 nm HV-CMOS
technology by the collaboration of Karlsruher Institut f\"ur Technologie (KIT),
Institut de F\'isica d'Altes Energies (IFAE), University of Liverpool and
University of Geneva. It includes two large monolithic pixel matrices which can
be operated standalone. One of these two matrices has been characterised at
beam test before and after irradiation with protons and neutrons. Results
demonstrated the feasibility of producing radiation hard large area fully
monolithic pixel sensors in HV-CMOS technology. H35DEMO chips with a substrate
resistivity of 200$\Omega$ cm irradiated with neutrons showed a radiation
hardness up to a fluence of $10^{15}$n$_{eq}$cm$^{-2}$ with a hit efficiency of
about 99% and a noise occupancy lower than $10^{-6}$ hits in a LHC bunch
crossing of 25ns at 150V.
