

Hierarchal Layout Editing Circuit designs typically consist of multiple instances of the same cell. An example would be the InverterTest design that you have created in the previous tutorial. Instead of having to redraw the same layout cellview multiple times in a higher level cellview, you can place completed layout instances in the design, similar to schematic editing. Since it is ensured that each of the cells function correctly by means of LVS, DRC verification and HSPICE or Nanosim simulation, placing layout instances not only saves time in drawing the cells, it means that the only errors that occur should result from connection errors. Layout Simulation
After you have verified that the layout matches the schematic, simulations can be performed on the extracted layout similar to the previous tutorial to determine its performance. The main difference between a schematic simulation and a layout simulation is that in a layout simulation,parasitic capacitances are extracted from the layout based on the physical dimensions and are used in the simulation. Therefore it