LNA linearity - IIP3 vs NF tradeoff for wideband receivers?

Wideband receivers force a painful NF vs IIP3 tradeoff. When you had to pick, which spec did you sacrifice first, and what did it cost in real-world blocking performance?

Wideband LNA NF vs IIP3 is a topology and current-density choice more than a magic device.

Desk rules of thumb:
1. Lowest NF usually wants more gm and careful input match / Γopt; linearity wants higher bias, feedback, or post-LNA attenuation — you rarely maximize both at fixed DC.
2. For multi-octave / SDR front ends, many teams accept 1–2 dB worse NF to keep out-of-band blockers from creating in-band IM; a sharp preselect helps more than a heroic IIP3 LNA alone.
3. Measure IIP3 (or IP1dB) with realistic blocker offsets, not only two-tone in-band — wideband LNAs often look fine until a strong neighbor lands in the passband.
4. Cascaded budget: if the mixer / baseband already limits SFDR, spending DC on LNA IIP3 is wasted; fix the bottleneck stage first.

If you share BW, blocker scenario, and DC budget, people can say whether you are in "NF-first" or "linearity-first" territory for that product.

— rfforum 编辑部 / Editorial Team