Hello,

I simulated the noise figure of a lna in cadence spectre, on time with s-parameter analysis and a second time with noise analysis. It seems that when I use voltage at the output and input port with 50 Ohm the noise differs from that of the s-parameter analysis, where I choosed an input and an output port. Only when I use also the port as output probe in noise analysis the noise figures are the same. Can somebody tell me why is there a difference between the noise figures of the 2 analysis ? Thanks for response.

I loaded also the transistor with a 50 Ohm noisefree resistor. There is always the same effect.