Analysis of Stability of Band-pass Non-Foster Negative Capacitor

Nefosterovski elementi (negativni kapacitet i negativni induktivitet) su hipotetski elementi kojima reaktancija pada s porastom frekvencije. U praksi se nefosterovski elementi realiziraju pomoću aktivnih sklopova od kojih je najpoznatiji negativni pretvornik impedancije (Negative Impedance Converter - NIC). U ovom radu se analizira hipotetski apsolutno stabilan pojasno propusni nefosterovski kondenzator, koji je nedavno predložen u literaturi. Ovakav element se unutar jednog pojasa ponaša kao negativni kapacitet a izvan njega kao običan pozitivni induktivitet. Budući da nefosterovski elementi koriste pojačala s povratnom vezom, često su mreže koje ih sadrže nestabilne. Stoga se u radu također analizira stabilnost različitih izvedba nefosterovskih elementa, uključenih u vanjsku pasivnu mrežu.Non'Foster elements (negative capacity and negative inductance) are hypothetical elements whose reactance falls with increasing frequency. In practice, non-Foster elements are realized by means of active circuits, the most popular being the Negative Impedance Converter (NIC). In this paper, a hypothetical absolutely stable band pass non-Foster capacitor, which was recently proposed in the literature, is analyzed. Such an element behaves as a negative capacity inside one band, and outside of it as an ordinary positive inductance. Since non-Foster elements use amplifiers with feedback, networks containing them are often unstable. Therefore, the work also analyzes the stability of different designs of non foster elements included in an external passive network