# Does anyone knows about LC filter

Joined Apr 14, 2016
9
Hello Everyone!!

I am getting confused with LC-filters (also with emi-filters). Capacitors eliminate noise from signals. It bypass it to ground or noise source.
The inductor does not allow high frequency to pass and also reduce current noise and I think it is correct but not sure??

Inductor reactance are linearly promotional to frequency and it is opposite for capacitive reactance. I am also familiar with frequency resonance ...
I studied first order RC-filters one time. I know how they work.

When I think of LC filters first it comes to my mind is that capacitor limit frequency but not sure what the inductor does?? Signals are DC square wives!!

Could you please tell me which one limit frequency and which one eliminate noises ??

Joined Mar 10, 2018
4,057
I am getting confused with LC-filters (also with emi-filters). Capacitors eliminate noise from signals. It bypass it to ground or noise source.
The inductor does not allow high frequency to pass and also reduce current noise and I think it is correct but not sure??
Depends where in circuit the complex element is -

Regards, Dana.

#### Audioguru

Joined Dec 20, 2007
11,249
Noise can be low frequencies, high frequencies or both. You are probably talking about high frequency noises. A lowpass filter passes low frequencies but reduces high frequencies.
An RC or LR lowpass filter reduces high frequencies gradually. An LC lowpass filter reduces high frequencies twice as much.