> On the subject of having objects on one layer effect the other layers: > > Some devices such as high frequency current feedback opamps (example: > AD8009) have a tendency to peak at the high frequency if their inverting > pin has capacitance associated with it. Even small amounts of parisitic > capacitance could cause these types of devices to occilate. So, all > other copper should be cept away from under them and other pads and > traces wich directly connect to them.
This may be usefull also for etched inductors. It would be nice to have some kind of forbidden zone when autorouting. > > A second example is the impedence characteristics of strip lines. The > impedence changes when you have a copper polygon/trace underneith and > when you have just free space. > > I am not advicating having PCB have the capability to do this > automatically. But it is one example of how objects on one layer are > effected by other layers. > > > > Steve Meier > Wojciech Kazubski
