  We present a compact physics-based model of the current-voltage
characteristics of graphene field-effect transistors, of especial interest for
analog and radio-frequency applications where bandgap engineering of graphene
could be not needed. The physical framework is a field-effect model and
drift-diffusion carrier transport. Explicit closed-form expressions have been
derived for the drain current covering continuosly all operation regions. The
model has been benchmarked with measured prototype devices, demonstrating
accuracy and predictive behavior. Finally, we show an example of projection of
the intrinsic gain as a figure of merit commonly used in RF /analog
applications.
