Re: gEDA-user: PCB Lines Over Polygons & Layer-groupings

[Wojciech Kazubski <wk@ire.pw.edu.pl>]

> 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