My layout for an analog signal circuit uses three layers.
I have a ground plane, top layer with signal traces, and one layer with power traces --- I have +15, -15, +5, and -5; all four voltages generated from a 5V input.
Does it make sense to split the ground plane into two separate planes, one for power (i.e., for the decoupling capacitors), and one for the components that connect the various signals to GND?
And since I only have a handful of those, I wonder whether the signals should use a star ground configuration, instead of a ground plane?
The only connections to ground for the signals come from one Sallen-Keys 2nd-order 1MHz low-pass filter (two connections, since it has some bandpass gain) and one AD8138 to produce a complementary/differential output (two connections --- one resistor that connects to GND and the Vocm input that's set to GND). Plus the grounds of the two output connectors. So, it will be rather easy to set up the star ground layout for these, where the center point is the (only) point that connects to the other layer with the ground plane.
Does this make sense? Please feel free to suggest any alternatives.