electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, a nullator is a theoretical

linear Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...

time-invariant In control theory, a time-invariant (TIV) system has a time-dependent system function that is not a direct function of time. Such systems are regarded as a class of systems in the field of system analysis. The time-dependent system function is ...

one-port In electrical circuit theory, a port is a pair of terminals connecting an electrical network or circuit to an external circuit, as a point of entry or exit for electrical energy. A port consists of two nodes (terminals) connected to an outside ...

''defined'' as having zero current and

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge t ...

across its terminals. Nullators are strange in the sense that they simultaneously have properties of both a short (zero voltage) and an

open circuit Open circuit may refer to: *Open-circuit scuba, a type of SCUBA-diving equipment where the user breathes from the set and then exhales to the surroundings without recycling the exhaled air *Open-circuit test, a method used in electrical engineering ...

(zero current). They are neither current nor voltage sources, yet both at the same time. {{cite book , author=Verhoeven C J M van Staveren A Monna G L E Kouwenhoven M H L & Yildiz E , title=Structured electronic design: negative feedback amplifiers , year= 2003 , publisher=Kluwer Academic , location=Boston/Dordrecht/London , isbn=1-4020-7590-1 , pages=§2.2.1.1 pp. 30–32 , url=https://books.google.com/books?id=p8wDptzCMrUC&pg=PA24 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

operational amplifier An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to ...

(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 operational amplifier. A nullator is normally paired with a norator to form a nullor. Two trivial cases are worth noting: A nullator in parallel with a norator is equivalent to a short (zero voltage any current) and a nullator in series with a norator is an open circuit (zero current, any voltage).

References

External links

Nullator article from Analog Insydes reference
Electrical components Control theory Signal processing Analog circuits Electronic design