Hi, I wrote a simulation of lock in amplifier using Matlab and now i want to test it for different SNR. I added to the signal white gaussian noise. In all the spec that i read, always written that the lock in amplifier can handle -100dB of noise. When I add a noise of SNR=-30dB the lock in stops working, when i look at the spectrum of the signal+noise i see that the component that i am looking for is covered by noise so no wonder that the lock in doesn't work. what i don't understand how is that in spec always written that lock in works at -100dB? i think that i am missing something. attached spec of lock in amplifier : http://infrared.als.lbl.gov/content/PDF/equipment/SR810830_specs.pdf look at the part of dynamic reserve. I didn't add any ADC and quantization yet. So the system only consist of sinus signal that is the signal and reference and Gaussian noise. Thanks for any help.