Hi Saandy,

"+100dBm second order intercept" means that second order distortion
products, following a simple small-signal second order model, would
become equal to the input if extrapolated up to +100dBm. Second order
products increase in dB amplitude exactly twice as fast as the
fundamental, so that means that, say, a -10dBm input would produce an
input-referred second harmonic of -120dBm, or -110dBc. If you decrease
the input to -20dBm, the second harmonic drops to -140dBm, or -120dBc.
If you increase the input to 0dBm, the second harmonic increases to
-100dBm, which is also -100dBc. Extrapolating those numbers, you get a
+100dBm second order intercept. In no way does it imply that the
preamp (not all that low noise at a 10dB noise figure) can put out
+100dBm, or can handle even +10dBm input without clipping or serious
compression (though it would be nice in this case to get to close to
that input level before clipping). Of course, distortion rises very
quickly as you go into compression/clipping.

Similarly, a +55dBm third order intercept implies third harmonic at
-110dBm for a 0dBm signal. In other words, I'm looking for an
amplifier that has about equally good second and third order distortion
products for inputs near full scale. I don't want super-good TOI
without also having second order products low.

Cheers,
Tom