Nanotransistors typically operate in far-from-equilibrium (FFE) conditions, that cannot be described neither by drift-diffusion, nor by purely ballistic models. An analytical model capable to describe the operation of transistors in FFE conditions would then be required in order to swiftly assess their performance and limitations. In addition, in carbon-based nanotransistors, source and drain contacts are often characterized by the formation of Schottky Barriers (SBs), with strong influence on transport. Here we present a model for one-dimensional field-effect transistors (FETs), taking into account on equal footing both SB contacts and FFE transport regime. Our model represents a significant advancement with respect to the currently available ideal or semi-ideal transport models. We show that the interplay of SB and ambipolar FFE transport gives rise to a number of features in device characteristics, often detected in experiments.