noise calculation question

[tyanata]

We design chip in which input signal is chopped at 4Khz. After amplification this signal is manipulated in ADC with sampling frequncy 1MHz. I have simulation results ( on PSpice) for the noise at 4KHz and 1MHz.

My question is:
Is there any rule to calculate (on the base of the noise at both frequncyies), the real noise disturbance of the useful signal?

 

[wholx]

try to calculate the SNR to measure the noise disturbance. for adc, there's a approximate formula useful for calculating the effect of the conversion on the SNR. just note that the SNR could vary in terms of the correlation between the signal and the noise.