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Increasing the nonlinearity of the scheme leads to a reduction of CNP

Question asked by Aleksandr001 on Jan 15, 2016
Hello! I use simple scheme, which consists of signal source and amplifier. I found that when the ratio Pout>=OP1dB integrated noise power (CNP) is reduced.
Signal source: CW, 100 MHz, 0 dBm, BW=1 MHz;
Amplifier: G=0 dB; NF=5dB; OP1dB = -10 dB;
In Spectrasys simulation shows that indeed the ratio Pout<OP1dB, the simulated result coincides with the value of CNP calculated by the formula Pnoise= - 174 dBm + 10 log(BW) + NF the value of CNP = -109 dBm.
But when you switch to the saturation of the amplifier the value of CNP begins to decrease and spectrasys displays the following message: "Part 'RFAmp_1' has been driven past the input saturation point of -7 dBm. The total input power is -0.00 dBm. Current element gain compression is 7.01 dB. Spectrum and measurements have less accuracy."
Please help find a solution to this problem! Thank you!