Queries about LC and RC filters.

[czech]

r c filter disadvantages

hi guys, i need help from u guys, i search the net but ddint get the answer to wad i want. my question is : What are the advantages and disadvantages of using a LC filter as compared to a RC filter? please help me. thanks :|

 

[Davood Amerion]

1- filter order of LC is twice of RC
2- RC filter consume power as heating loss but LC is lossless

 

[Kral]

czech,
If you are referring to stricly passive RC filters, then here are some disadvantages:
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Can not implement the classic filter types, such as Butterworth, Chebyshev, Legendre, Bessel, etc.
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Maximum "Q" is 0.5.
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If you include active RC filters, then here are some advantages:
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Filter characteristics do not depend on load resistance.
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Capacitors are phsically smalller than inductors at low frequencies.
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The main disadvantage of active RC filters is that the gain-bandwidth product must be much higher than the maximum frequency of interest. This limits their applicaltion to relatively low frequencies.
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Disadvantages of LC filters:
~ Must be designed for specified source and load reistances.
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~ Inductors that are close to ideal inductors are difficult to design, so the final design must be "tweaked" to allow for finite Q, distributed capacitance.
~ Inductors for low frequency applications are physically large.
Regards,
Kral

 

[czech]

thnx for the reply. wad abt advantages of LC filters? anyone?? i mostly understand wad u guys talking abt..

 

[Kral]

czech,
For a given number of components, twice the filter order can be obtained as with RC filters. This means twice the attenuation slope (db/decade).
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Can be impolemented for high frequency operation.
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No power required (as opposed to active RC)
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Rugged. Can take abuse such as voltage surges.
Regards,
Kral

 

[electronics_kumar]

czech,
.
~
Capacitors are phsically smalller than inductors at low frequencies.
~
Regards,
Kral

kral
I unable to digest the fact prvided by you..at low frequency cap will be large not small as indicated by you and it will decrease if frequency is increased.