As generally recognized, the performance of a CMOS gate, such as propagation delay time or short circuit power dissipation, is strongly affected by the nonzero input signal transition time. This paper presents an analytical model of the transition time of CMOS structures. The authors first develop the model for inverters, considering fast and slow input signal conditions, over a large design range of input-output coupling capacitance and capacitive load. They then extend this model to more complex gates. The validity of the presented model is demonstrated through a comparison with HSPICE simulations on a 0.18 /spl mu/m CMOS process.