  This work presents a depleted monolithic active pixel sensor (DMAPS)
prototype manufactured in the LFoundry 150\,nm CMOS process. DMAPS exploit high
voltage and/or high resistivity inclusion of modern CMOS technologies to
achieve substantial depletion in the sensing volume. The described device,
named LF-Monopix, was designed as a proof of concept of a fully monolithic
sensor capable of operating in the environment of outer layers of the ATLAS
Inner Tracker upgrade in 2025 for the High Luminosity Large Hadron Collider
(HL-LHC). This type of devices has a lower production cost and lower material
budget compared to presently used hybrid designs. In this work, the chip
architecture will be described followed by the characterization of the
different pre-amplifier and discriminator flavors with an external injection
signal and an iron source (5.9\,keV x-rays).
