Taming injected common-mode noise

摘要

External noise sources inject signals into analoginput circuits at every opportunity. Good grounding practice, prudent use of shields, decoupling capacitors, separate analog and digital grounds, Faraday-shield traces, and controlling noise sources minimize noise problems, but these tricks don't eliminate noise. The input circuit interfaces with the real world so noise always creeps into this circuit, and Murphy's law dictates that noise and signal amplitudes are often inversely related.