Difference of RC and LC filters

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Spectacular Butter said:
Hi may i know what's the difference between using a RC and LC filters besides difference in components? Thanks a lot.
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An LC filter has a steeper slope, because it has two 'active' components rather than just one. Generally you would use RC in an opamp filter, because it's far easier (and cheaper) to obtain resistors than high value inductors, and the opamp makes up for not using inductors. For a passive filter (crossovers etc.) you would usually use LC for the much greater performance.

What sort of filter are you asking about?.
 
Spectacular Butter said:
i am using it for RF filters (high pass and low pass)
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RF filters will be LC, you wouldn't want to use an RC filter for RF, there's really no point!.
 
Both inductors and capacitors are passive components, they are active in a sence that they both react to frequency.

As frequency goes up small inductors are used, so it is practical to use them in RF.

Active filters are always going to be better not only for the octave or decade slope, but are very tunable over passive filters.
 
There is less power dissipated in a LC circuit than an RC circuit. RC is fine for filtering low power signals but when you are trying to filter a high power signal, like RF, LC is better suited.
 
LC circuits will resonate at a specific frequency.
RLC circuits will resonate over a wider range of frequencies.
RC circuits are small and cheap.
RL circuits are large and expensive. I don’t recall ever encountering one in the field except as a side effect of a transformer.
 
Nigel Goodwin said:
An LC filter has a steeper slope, because it has two 'active' components rather than just one.
Click to expand...
Nigel, perhaps the term "reactive" would be a better term since "active" is usually used to describe amplifiers, transistors etc.

Certainly for RF you would use LC filters since they give better performance and the inductors and capacitors are small and inexpensive at RF frequencies.
 
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