The paper describes a new technology-independent model for the large-signal performance prediction of electron devices. The Nonlinear Integral Model (NIM) is rigorously derived from the Volterra series through suitable modifications so that fast convergence can be achieved even under large-signal strongly nonlinear operation. In particular, the NIM, which can be directly used for Harmonic-Balance circuit analysis, enables the large-signal dynamic response of electron devices to be directly computed on the basis of data obtained either by conventional measurements or physics-based numerical simulations. This property makes the NIM particularly convenient for linking accurate device simulation based on carrier transport physics and Harmonic-Balance circuit analysis. Simulations and experimental results confirm the validity of the proposed modelling approach.