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Whats the error in attached band pass filter?

screamer

Jan 10, 2012
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I have attached a bandpass filter I have constructed and simulated. The frequency range of the band pass filter is 704 Hz to 2040 Hz. But the problem is even when I put 60Hz I am still getting the same input wave at the out. So, what's wrong with the circuit. (Please explain in a simple and easy way to understand, cuz I am a newbie). If theres something wrong can I get a correction.
 

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  • Bandpass Filter.png
    Bandpass Filter.png
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  • Bandpass Filter Output.png
    Bandpass Filter Output.png
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Laplace

Apr 4, 2010
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What does the Bode plot of that bandpass circuit look like? Can you post a picture?
 

Harald Kapp

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Nov 17, 2011
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I simulated your circuit with LTSPICE. I'm getting the expected bandpass response, see attachment.
Probably something wrong with your simulator setup?

Harald
 

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duke37

Jan 9, 2011
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You say that the first filter has a turn over frequency of 704Hz but you have two loading resistors effectively in parallel, giving half the load resistance, hence a turn over frequency of 1408Hz.
 

Harald Kapp

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Right,
R1 and R2 are effectively in parallel. Also the impedance of the low-pass part of your filter poses a burden on the high-pass that is not negligible. You can reduce the influence of the low-pass impedance on the high-pass by using larger resistor and, accordingly, capacitor values for the low-passs part.

Harald
 
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