Hello, I am investigating the noise characteristics of the THS4131, to start with I am using Tina-TI with an example. The example that I loaded was 'C:\Program Files (x86)\DesignSoft\Tina 9 - TI\EXAMPLES\TI Test Circuits\THS4130.TSC'.
When I run a noise analysis I see noise at ~35 nV/sqrt(Hz) for the common mode measurement, but only 3.82 nV/sqrt(Hz) for the differential measurement (VM1?) (at 10 kHz). When referred to the input, the differential noise measurement at 10 kHz is 1.95 nV/sqrt(Hz), a bit lower than the spec limit of 1.3 nV/(sqrt(Hz)). Is that deviation within reason ?
My bigger question is why the common mode noise is so high, I am wondering if this is a real result. This was a bit surprising to me since I didn't see this phenomena mentioned in the app notes. Is that expected with this differential amplifier ? If so, what precautions should I take to ensure the common mode noise never works its way into the system ? The planned destination is a differential ADC, with a few more diff gain stages and a diff antialias filter.
Any pointers/help is appreciated.
