nihajni krog kot filter

[roger]

Slišal sem, da se lahko električni nihajni krog uporabi kot filter. In sicer naj bi dobro prepušal ozko območje okrog neke določene frekvence. Menda zaradi tega, ker ima impedanca nihajnega kroga resonančno obliko. Kaj je pravzaprav impedanca nihajnega kroga in zakaj bi to omogočalo prepuščanje samo nekih frekvenc?

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Gre za resonančni filter:

http://www.allaboutcircuits.com/vol_2/chpt_8/6.html.

P.S. O impedanci nihajnega kroga si lahko prebereš tukaj:

http://en.wikipedia.org/wiki/LC_circuit ... C_circuits.

[Mafijec]

Kaj ni tak, da se za filtre uporabljajo ponavadi R in C? L pač ni najbolj priljubljen eletronski element...

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Zakaj pa naj bi bila tuljava nepriljubljen element? Gledam npr. navodila ojačevalca, ki ga imam v svojem konjičku, in čisto za vsako vezavo zvočnikov je v kretnici vsaj ena tuljava.

[Aniviller]

Problem je predvsem, da tezko naredis tuljavo brez upora in da se na vezju rade sklapljajo. Nisem elektronik, zdi se pa mi, da za uporabo znotraj kompleksnih vezij, ki opravljajo kaksno precizno numericno dejavnost niso tako zazeljene, tako da se pojavijo predvsem v enostavnih vezjih za uravnavanje napetosti in tam, kjer so tokovi vecji.

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Če govorimo o filtriranju, so v določenih primerih nizkoprepustni filtri s tuljavo boljša izbira:

The inductive low-pass filter is the pinnacle of simplicity, with only one component comprising the filter. The capacitive version of this filter is not that much more complex, with only a resistor and capacitor needed for operation. However, despite their increased complexity, capacitive filter designs are generally preferred over inductive because capacitors tend to be “purer” reactive components than inductors and therefore are more predictable in their behavior. By “pure” I mean that capacitors exhibit little resistive effects than inductors, making them almost 100% reactive. Inductors, on the other hand, typically exhibit significant dissipative (resistor-like) effects, both in the long lengths of wire used to make them, and in the magnetic losses of the core material. Capacitors also tend to participate less in “coupling” effects with other components (generate and/or receive interference from other components via mutual electric or magnetic fields) than inductors, and are less expensive.

However, the inductive low-pass filter is often preferred in AC-DC power supplies to filter out the AC “ripple” waveform created when AC is converted (rectified) into DC, passing only the pure DC component. The primary reason for this is the requirement of low filter resistance for the output of such a power supply. A capacitive low-pass filter requires an extra resistance in series with the source, whereas the inductive low-pass filter does not. In the design of a high-current circuit like a DC power supply where additional series resistance is undesirable, the inductive low-pass filter is the better design choice. On the other hand, if low weight and compact size are higher priorities than low internal supply resistance in a power supply design, the capacitive low-pass filter might make more sense.