Simulating Active Bandpass Filter Example from Textbook in Simulink

Hello!

I'm an electrical engineering student and is fairly new with MATLAB.

I had tried to simulate a fourth-order butterworth low-pass filter example with the cutoff frequency of 500Hz from a textbook. But the result was not like what I had expected.

Here's my circuit: Vi = 100sin(2*pi*100*t), f = 100Hz

Here's the plot of Vi and Vo:

What I was hoping, Vi and Vo is sinusoidal.

But, as you can see from the scope, it is clearly not.

My question is, did I set something wrong? Maybe something that had to do with advanced settings and so on.

I'm know that it is better to ask this kind of question at other online electrical engineering forums. But, since that this is an example from textbook, my only idea is there's something wrong with the settings or something similar.

Thank you in advance and I'm very sorry if my English is bad.

[Pat Gipper]

If the circuit was assembled per the picture then it will work as you expect. No advanced settings are required. Double check the values for R & C.

[Zuhri Ashraaf]

Checked and eveything is correct.

However, when I change the AC voltage source with a controlled voltage source that are connected to sine wave block, everything went great.

Now, I am more confused than before.

What is the difference between the AC voltage source and the controlled voltage source that are connected to a sine wave?

Answer 1

[Priyank Pandey]

Hi Zuhri,

The above circuit is correct and idealy it should give the desired output of the waveform.

You can refer to the following links to understand the difference between controlled voltage source and

AC voltage source.

Implement controlled voltage source - Simulink (mathworks.com)

Implement sinusoidal voltage source - Simulink (mathworks.com)

Also you can refer to Build a Low-Pass Filter by Using Fixed-Point Data - MATLAB & Simulink (mathworks.com) to learn more about low-pass butterworth filter.