Hello,
this question has been asked 4 years ago, but since then no answer came up. I'm trying to simulate the noise at the output of this simple circuit
I've imported the model download from the Analog Device website and included in TINA spice. I'm getting the same results also with LT-Spice, so it is not a problem of the simulator.
The noise at the output of the circuit is the following:
Which makes no sense. First of all, I don't see any 1/f noise. Second, the flat part is 18.68 nV/sqrt(Hz).which is wrong. Indeed, if I do the calculations on my own and consider only the white noise, I get the following contributions:
Consider RG1=RG2=RG and RF1=RF2=RF
1) RG1 and RG2
Sout = 2*4*KT*RG*(RF/RG)^2 = 2*4*KT*RG = (2.5 nV/sqrt(Hz))^2
2) RF1 and RF2
Sout = 2*4*KT*RF = (2.5 nV/sqrt(Hz))^2
3) AD8139
Sout = Sv*(1+RF/RG)^2 + 2*Si*RF^2 = 2*Sv + 2*Si*RF^2 = 2*(2.25 nV/sqrt(Hz))^2 + 2*(2.1pA/sqrt(Hz))^2*(200)^2 = (3.2 nV/sqrt(Hz))^2
By summing all the individual contribution I get
Sout = (2.5 nV/sqrt(Hz))^2 + (2.5 nV/sqrt(Hz))^2 + (3.2 nV/sqrt(Hz))^2 = (4.8 nV/sqrt(Hz))^2
which is way different.
Can you help me?
