Thevenin / Norton Converter

Léon Charles Thévenin was a French telegraph engineer who published his equivalent-circuit theorem in 1883 in the Annales Télégraphiques. Thévenin was actually working on telegraph-cable analysis, not building a theoretical framework, and his paper went largely unnoticed outside France for decades. Similar ideas had been worked out by Hermann von Helmholtz thirty years earlier in 1853 — so in some European textbooks the theorem is called the "Helmholtz-Thévenin theorem."

Edward L. Norton, a Bell Labs engineer, formalized the current-source dual in a 1926 internal memo that was never externally published during his lifetime. The theorem was rediscovered and popularized in the 1930s-40s in MIT and Bell System textbooks. Hans Mayer in Germany had independently published the same result in 1926, which is why in German-speaking engineering literature the theorem is often called "Mayer-Norton."

Together, these theorems reduce arbitrarily complex linear networks to a two-component equivalent — a profound simplification that makes load-line analysis, maximum power transfer calculations, and driver/receiver impedance matching tractable. Every modern op-amp input model, every output stage spec sheet, every battery-impedance measurement invokes Thévenin implicitly. For power engineers, the Thévenin source impedance at a given bus governs the fault current available there.

Pick the source representation (Thévenin or Norton), enter either Vth or In along with Rth (= Rn). The tool computes the other form using Vth = In × Rn, returning both representations along with short-circuit current and optional load voltage. If you supply RL, the tool computes V_load = Vth × RL/(Rth + RL).

Maximum power transfer occurs when RL = Rth: Pmax = Vth² / (4·Rth). Efficiency at max-power-transfer is only 50% because half the power is wasted in Rth — audio and power amplifiers deliberately operate with RL > Rth (typically 8×) to favor efficiency over power. Everything runs client-side; no values leave your browser.