why noise analysis is done in integrated circuits?

[techguru]

Hi to all,
        can any body explain why noise analysis is done in integrated circuits?

[brabus]

Usually the goal is to have as little noise as possible, so the noise analysis helps you predict how much noise will your IC produce. Would you buy a very noisy OpAmp, for example? Even it if was cheap?

The question is actually non trivial, let me turn it: why is noise analysis [usually] skipped on discrete design? Well, if your discrete design happens to be noisy, you can modify it by changing some parts and pursue your SNR goal.

But if an IC is noisy, there is not really much left to do than change it.

[pwlps]

If you deal with clean Volt-range signals then you don't care about noise analysis but for very small signals (e.g. of order of microvolt or smaller in a radio receiver front-end) the noise added by the component itself is a problem.  For example the GPS signal can be 40dB below the thermal noise level, therefore selecting low-noise components for the receiver is important.