In this paper, we have proposed a new analytical model for FETs working in the quasi-ballistic regime. The model is based on a calculation of the charge density along the channel which is then used to solve Poisson's equation to get the variation of the channel potential. This is then used to calculate the ballistic and drift-diffusive components of the current. The model is capable of accurately predicting the terminal I-V characteristics for all drain and gate biases and includes short-channel effects. It takes length scaling into account and can be used for the full range of devices starting from complete drift diffusive to completely ballistic. The model has been verified with data for high electron mobility transistors (degenerate) and common multigate and nanowire FETs (nondegenerate) proving its ability to take different geometries into consideration. It can be easily implemented as a compact model and used for SPICE circuit simulations.