Is the Gain 9.4dB or 18.8dB?

[tony_lth]

Hi, Gurus,
I am confused about the gain of an OpAmp.
As attachemnt, when I simulated the Gain of an opa,
the trace expression is (dBm(Vout[::,1])-dBm(Vin[::,1])), so I get 9.4dB gain.
But this 9.4dB is much less than the gain tested with VNA.
I think VNA tested is power, so it should be V^2/R, then the foresaid gain expression should be 2*(dBm(Vout[::,1])-dBm(Vin[::,1])), i.e. 18.8dB gain in dBm.
Am I right?
Best,
Tony Liu

 

[FvM]

Completely wrong. Gain of 9.5 dB is either factor 3 voltage gain or factor 9 power gain. The value must not be doubled when switching from power to voltage gain.

Source and load impedance however matters for the measurement. Without knowing your setup, we can hardly guess about the problem.

 

[dick_freebird]

RF tends to speak in power and analog in voltage gain. dBm is always power, db10. That is not appropriate for an op amp small signal gain (db20, voltage).