A compact model for the Carbon nanotube transistor (CNFET) is presented in this work. This simple model aids the first-order analysis for digital and analog design with CNFET. Based on the physical understanding of ballistic transport in the CNFET channel and tunneling at the Schottky barrier contacts, we develop a set of closed-form expressions that predict the device behavior with varying process and bias conditions. Using this model, we compare a CNFET with 22nm MOSFET in both digi-tal and analog domains. We conclude that (1) a CNFET digital circuit can be more than 10X faster than 22nm CMOS; (2) there is 10X improvement in gm for compara-ble device dimensions, and (3) >25X improvement in gDS for comparable saturation current. This simple, scalable model is an efficient tool for analytical treatment of CNFET based circuits, revealing potential design oppor-tunities, especially in the analog domain.