gEDA-user: pcb, how to make windows in ground and power planes?

[Stefan Salewski <mail@xxxxxxxxxxxx>]

For multilayer pcb layout it is sometimes recommended to make windows in
ground and power planes near pins/pads of high speed OpAmps, see
datasheet of OPA656 page 14:

a) Minimize parasitic capacitance to any AC ground for all
of the signal I/O pins. Parasitic capacitance on the output and
inverting input pins can cause instability—on the noninvert-
ing input, it can react with the source impedance to cause
unintentional bandlimiting. To reduce unwanted capacitance,
a window around the signal I/O pins should be opened in all
of the ground and power planes around those pins. Other-
wise, ground and power planes should be unbroken else-
where on the board.

Is there a way to to make such windows for pcb, or have I to build the
planes from tiny rectangles? (I have a 6-layer pcb, all OpAmps are SMD,
second layer is groud plane.)

Nest regards

Stefan Salewski




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