Test filter response on Schematics

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Hello all. I have worked out a 1st order low pass Butterworth filter for a load of 5 Ohms and cut-off frequency of 60 Hz and I have used the First Cauer form to implement the LC filter. I have calculated values of input inductance (L1), shunt capacitance(C1) and output inductance(L2). I want to obtain the frequency response of the filter on Schematics. I want to know where the actual cutoff frequency is.

Any ideas how I can simulate and find this response?? I will be using this filter with another circuit later..

:|:?::?:
 

Just simulate it with any Spice simulator. Most free demo versions will do that or LTspice.

Keith.
 


My recommendation for you is to become familiar with the topics filter theory.
A first order filter canot have a Butterworth response. More than that, an LC filter has a minimum order of two! Later you speak of L1 and C1 and L2, which corresponds to an order of three! Compare this with your first sentence (1st order).
 

To help you further with SPICE simulation. I am attaching an example showing step by step approach to simulate a low pass filter. Once you understand the steps you can simulate any filter.

Hope it helps
-Hemanshu
 

Thanks Hemanshu..

@LvW.. sorry i wrongly put the order..its a 2nd order filter.. I have managed to work it out thanks again..
 

abbeyromy said:
To help you further with SPICE simulation. I am attaching an example showing step by step approach to simulate a low pass filter. Once you understand the steps you can simulate any filter.
Hope it helps
-Hemanshu
Click to expand...

Just two comments to the presented step-by-step approach:
* Point 1: 10001 points/dec is not necessary (too time consuming); 100 points/dec are sufficient
* Point 4: The 3-dB-point is not for all second (or higher) order filters identical to the characteristic bandwidth. See the bandwidth definition for (elliptical) Cauer and Chebyshev responses.
 

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