We present a physical approach to model the Dual Gate CNTFET. In this transistor, whose type (N or P) depends on the Back Gate bias, the charge of each region (source and drain accesses and inner part) remains an essential quantity to evaluate the channel potential and thus the drain current. The charges are calculated (i) considering 0 or 1 carrier transmission probability and (ii) assuming that the carrier energy is not affected by backscattering mechanisms to obtain a physical compact description. Using this compact model, typical electrical characteristics of such transistor are presented.