This paper presents an analytical modeling of ballistic and quasi-ballistic transport, implemented in Verilog-A environment and used for circuit simulation. Our model is based on the Lundstrom's approach and uses an expression of the backscattering coefficient given by the flux method. The model takes also into account short channel effects and tales into account the effects of different scattering processes through a dynamical mean free path. Using this model, CMOS inverters and ring oscillators have been simulated to highlight the impact of ballistic and quasi-ballistic transport on static and transient performance.