Memristor has turned into a popular nonlinear circuit element following the discovery of a thin-film system that mimics the behavior of a memristor. Some memristor research has concentrated on developing new memristor models. Some memristor models have window functions. In the literature, there are a lot of different window functions proposed for modeling them. Recently, it has been shown that some memristive models cannot do a complete resistive switching in a finite time and a window function with a finite resistive switching time has been suggested to model a memristor. In this paper, its Spice model has been given. The model is modified using a different shaping factor for each polarity. Its Spice model is made in the LTspice program. As an example, the model is used to simulate a memristor-based sawtooth generator in this study. Its simulation results are also presented to verify the circuit’s operation as a sawtooth signal generator.