In this paper the issue of obtaining an accurate equation for the delay of a CMOS inverter is explored. In the conventional equations provided for the propagation delay, many simplifying assumptions are made. Also some important events that occur during the charging/discharging of the capacitances are neglected. This reduces the accuracy of the conventional delay equations. Since the propagation delay time is used in many applications, such as obtaining the ring oscillator frequency, its accuracy is very important. Hence, we calculate an accurate equation for the propagation delay time. The intricacies and challenges in deriving an improved accuracy equation will be addressed. The approach of deriving an improved equation is explained in detail. The accuracy of the derived equation is verified through simulation. We will look into the obtained equation to evaluate the effect of different parameters on the delay and compare the improved and conventional equations.

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