I haven't found a single document that talks about "Gain Compression" in a power amplifier referring to the typical Ids vs Vds curve. Books talk about a sinusoid "clipping" when showing these curves but never use the term "compression". "Compression" is only used when showing gain vs input power or output power vs input power but is never mentioned when describing the Ids vs Vds curves. Why is that?
Can someone tell me where does compression start to occur on one of these curves and why would gain start to drop at this location?