Input and Output noise analysis giving different results

[richaphy]

I have done noise analysis for my low pass filter. When I am ploting the curves for noise, the output noise curve gives smaller amount of noise compared with the results I get from the input noise.
My filter has a cutoff frequency of 14Hz and fundamental frequency is 10Hz.
Please help me to understand which one is correct.
If any of these curves are currect or not.
What possible mistake I might be doing?
Thanks
Richa

 

[Audioguru]

The input noise curve shows noise beginning at 10kHz and increases a lot to 1MHz.
The output noise curve shows a lot of low frequency noise maybe from the opamps and resistors. This low frequency output noise reduces to nothing at 100Hz which is the result of the filter.

 

[Dominik Przyborowski]

Your simulations showing rapidly grow of input referred noise, because it is calculated as output noise PSD divided by transfer function. For high frequencies your gain going down so automatically input PSD is growing.

For low frequencies your noise PSD is determined by flicker noises which exists for all devices instead of metal resistors.