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Basic : Help me understand the LC low pass Filter.

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pawan kumar

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Hello Friends,

I know, it's late to ask this question which should have been silly 6 years ago.

Please help me understand this at least now.

LC low pass schematic.JPG

The image above is that of an LC low pass filter. On running an AC frequency response analysis, there is an increase in Voltage before it starts rolling off.

LC low pass waveform.JPG

I analyze the circuit by calculating it's transfer function which is

Vout/Vin = 1 /(1+W^2LC)

here I intend to mean omega as 'W'.
I am not able to understand how there can be an increase in voltage when there is no Amplifier attached to it.

Thanks in advance for your help.
 

FvM

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I analyze the circuit by calculating it's transfer function which is

Vout/Vin = 1 /(1+W^2LC)
The transfer function is wrong. Should be H(ω)= 1/(1-ω²LC).

Respectively the output voltage of the lossless and unloaded LC circuit at resonance frequency is infinite.
 

KlausST

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Hi,

Read obout "LC resonator" or "resonance frequency"

Klaus
 

pawan kumar

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Thanks FvM and KlausST.

I got the mistake. and as you said, I tried simulating the filter with a series resistance. It behaves as it is shown in the books..
 

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