Signaling Models#

What exactly is the signal, and what is it measured against? Every signal needs a go path and a return path; the way those paths are arranged is a fundamental design decision that determines noise immunity, cost, and complexity. These concepts cut across every domain — audio, RF, digital, and instrumentation — and getting them wrong is the root cause of most noise, grounding, and interference problems.

What This Section Covers#

  • Go & Return Paths — Every signal is a closed loop. Return path is not “ground.” Why splitting grounds breaks signals.
  • Reference Planes & Grounds — Ground is a reference, not a destination. Local vs global, chassis vs signal, floating vs earth-referenced.
  • Single-Ended vs Differential — Signal = V(A) - V(B). Single-ended is just a special case. Why symmetry matters more than shielding.
  • Balanced vs Unbalanced — The physical implementation: how balance enables common-mode rejection, and when it breaks.
  • Common-Mode vs Differential-Mode — Noise taxonomy. What common-mode noise really is, why CMRR is finite, and how imbalance converts one to the other.
Backward Conservation of Energy Go & Return Paths Forward