RE: How to fix your simulations when the macromodel’s voltage noise doesn’t match the datasheet

Cole Macias — Mon, 10 Oct 2016 21:26:25 GMT

Hey Clive,

Adding a resistor in series with the positive input would definitely be an alternative in this confirguration. Great point.

I like the use of a voltage noise source because you quickly run other tests without "upsetting your other measurements" like you mentioned. For example, if you were to build the circuit mentioned in the blog and then the build the circuit you are proposing, you will find that the DC analyses are different. In addition, the circuit with the voltage noise source will match the DC response of the macromodel with no noise correction. I encourage you to try it and ask why.

-Cole

RE: How to fix your simulations when the macromodel’s voltage noise doesn’t match the datasheet

Clive Read — Mon, 10 Oct 2016 11:05:37 GMT

Would an alternative be to add a resistor in series with the positive input?

The resistor value is given by R = (Vn)^2 (0.13)^-2

To get 30nV per root hertz you would need R = 30^2 x 0.13^-2 which is ~53kohms.

The resistor should only be there for noise measurement as it will clearly upset most other measurements.

Clive Read.