We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range.

The 1st stage LNA has to be the most sensitive---but what is important to consider when choosing a 2nd stage LNA?

This is the 1st stage LNA we are considering: Qorvo QPL9547

  • \$\begingroup\$ If you have headroom in the noise, go for gain. If not, impedance match for minimum noise. \$\endgroup\$ – user110971 May 17 at 1:44
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    \$\begingroup\$ P1dB, to allow you to handle strong signals. That is, linearity over your dynamic range. \$\endgroup\$ – SteveSh May 19 at 1:23
  • \$\begingroup\$ What other devices are in your receive chain, besides the amplifiers? \$\endgroup\$ – SteveSh May 19 at 1:24
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    \$\begingroup\$ If the gain is not constant and varies with the input signal power you have a non linearity. You could say that the gain is constant up to the P1dB (or some headroom before it). So if P1dB is high the amplifier is linear with a higher signal. \$\endgroup\$ – Mike May 19 at 6:03
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    \$\begingroup\$ @KJ7LNW - Yes, that's right about the amplifier going into saturation (another term for compression). When an amplifier compresses, it's operation is non-linear and can produce distortion, harmonics and intermodulation (intermods) products. So if you have two signals, one strong and one weak, and the stronger signal drives the amplifier into compression, the weaker signal will experience those same non-linearity effects. \$\endgroup\$ – SteveSh May 19 at 19:12

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