| OCR Text |
Show 93 circuit is ideally a smaller faster logic circuit such as an ECL part, where there are questions about the critical paths in the circuit. They will have been identified from a schematic simulation, and an ACRE program will be looking for those paths to extract for the sake of making a detailed RC analysis for a simulator such as Pspice. ACRE Analysis with Different Kinds of Substrates Because ACRE does not have Boolean operations to determine the substrate that two paths are over, it needs to have that step done in a preprocessing stage. Paths that are over certain substrates are put on distinct layers, and the formulae can recognize those layers when the parasitics are derived. Consequently different substrates and the dramatically different results between insulating and conducting substrates are relegated to the analysis of the formulae that are used to within ACRE. This is the most obvious consequence of the limitation that the comparisons of ACRE are pair-wise comparisons, because there are really two paths and the substrate needed in the analysis of a three way set of geometric interactions. Where paths are over an insulating substrate, they do not have a coupling with the substrate, but they have a much increased coupling with each other. Where they are over a semiconducting substrate, they have a much increased coupling with the substrate and a reduced coupling with neighboring geometries. The lines of flux that emanate from the paths are either stopped by the substrate giving a coupling to it or they extend to neighboring geometries for |
