  I present a compact physics-based model of the drain current, charge and
capacitance of graphene field-effect transistors, of relevance for exploration
of DC, AC and transient behavior of graphene based circuits. The physical
framework is a field-effect model and drift-diffusion carrier transport
incorporating saturation velocity effects. First, an explicit model has been
derived for the drain current. Using it as a basis, explicit closed-form
expressions for the charge and capacitances based on the Ward-Dutton partition
scheme, covering continuosly all operation regions. The model is of special
interest for analog and radio-frequency applications where bandgap engineering
of graphene could be not needed.
