The dynamic MOSFET model we have presented so far assumes the transistor to be in quasi-static operation, i.e., the charge densities at any position in the channel are assumed to depend on the instantaneous values of the terminal voltages only [1], [2], [3]. If, however, the rate of variation of the terminal voltages is high, the quasi-static approximation is no longer valid. In fact, the charge densities along the channel depend not only on the voltage values at a certain time but also on the history leading to the charge densities at that time [2]. The model used for fast varying signals is called the non-quasi-static model, which is the subject of this chapter.Chapter 8. High-Frequency Models Section 8.3 Non quasi-static small-signal model