Post Layout Simulation
The parasitic capacitances extracted according to how your layout is designed might be critical in affecting the actual performance of your design. In order to get an idea of how the design would work from your layout, you should perform a post-layout simulation from the extracted view. The procedure is identical to that for simulating from the schematic view.
Open the test schematic for the inverter you used in schematic view simulation.
Open the Analog Design Environment to simulate the circuit
For post layout simulation, an only different thing, compared with schematic view simulation, is that we need to change some set-up in environment as follows. In Analog Design Environment, choose Setup -> environment. If then, Environment Options will pop-up.
Type in ¡°extracted¡± on Switch View List in the Environment Options. It means that when simulating your circuit, the simulator will use extracted view¡¯s net-list, not net-list from schematic view. The other steps are same as that of the schematic simulation.
To compare both results of schematic view and extracted view, we need to overlap both results in a same window. Here is one example for this.
Use Plotting mode options. After you display your result from schematic simulation, simulate again with extracted view, and then switch to Append mode in Plotting mode as shown in figure below. Display again.
Finally, we will see two overlapped signals in a same window. If your layout is bad, the results show big differences between schematic and extracted view.