A simple analytical model to predict the DC MOSFET behaviour under electromagnetic interference (EMI) is presented. The model is able to describe the MOSFET performance in linear and saturation regime under EMI disturbance applied on the gate. The model consists of a unique simple equivalent circuit based on a voltage dependant current source and a reduced number of parameters which can accurately predict the drift on the drain current due to the EMI source. The analytical approach has been validated by means of electric simulation and measurements and can be easily introduced in circuit simulators. The proposed modelling technique combined with the nth-power law model of the MOSFET without EMI, significantly improves its accuracy in comparison with the nth-power law directly applied to a MOSFET under EMI impact.