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Old 03-23-2011, 08:51 PM
turkeybuzzard turkeybuzzard is offline
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Default LC bandstop theory

Hi -- I'm a novice and am trying to work out a theoretical problem. I put this question here because I figure you guys are the LC filter experts:

1. If I have a ideal AC source (at frequency f) connected to a series consisting of R,F,R,F,R (where Rs are equal resistance and Fs are LC parallel band stop filters tuned to frequency f) then what's the current across the resistors and what's the oscillating current inside each F. Is there no voltage drop across the Rs at the resonant frequency? Are the resonance currents inside the two Fs equal?

Here's the circuit:

Thanks for your thoughts,
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Old 03-25-2011, 05:33 AM
t_n_k t_n_k is offline
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If these are all ideal elements one would expect zero source current at resonance. Each parallel stop filter would see half the source voltage with two such branches. If there were three branches each would support 1/3 of the source voltage. So each parallel branch element would have a current proportional to the source voltage. The currents in the L&C components would be of equal magnitude but exactly out of phase at resonance.
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Old 03-25-2011, 06:42 AM
turkeybuzzard turkeybuzzard is offline
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T_N_K thanks for the clear response ... that makes sense.
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Old 03-28-2011, 03:58 AM
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Bill_Marsden Bill_Marsden is offline
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This is very similar to a thread (including the image) in the electronics chat area.

Beginner question about LC filters
"Good enough is enemy of the best." An old engineering saying, Author unknown.

General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input. Thanks for the verbage Wookie.
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