Nullator

In electronics, a nullator is a theoretical linear, time-invariant one-port defined as having zero current and voltage across its terminals. Nullators are strange in the sense that they simultaneously have properties of both a short (zero voltage) and an open circuit (zero current). They are neither current nor voltage sources, yet both at the same time.[1]

Inserting a nullator in a circuit schematic imposes a mathematical constraint on how that circuit must behave, forcing the circuit itself to adopt whatever arrangements needed to meet the condition. For example, the inputs of an ideal opamp (with negative feedback) behave like a nullator, as they draw no current and have no voltage across them, and these conditions are used to analyze the circuitry surrounding the opamp.

A nullator is always paired with a norator to form a nullor.

References

1 ^ Verhoeven C J M van Staveren A Monna G L E Kouwenhoven M H L & Yildiz E (2003). Structured electronic design: negative feedback amplifiers. Boston/Dordrecht/London: Kluwer Academic. pp. §2.2.1.1 pp. 30–32. ISBN 1402075901.