Author Topic: All pass filter simulation question  (Read 473 times)

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Offline lokajaudioTopic starter

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All pass filter simulation question
« on: June 12, 2021, 12:42:15 pm »
Hello all, i am currently simulating this circuit is LTspice

here is link:
https://www.rfwireless-world.com/Terminology/All-Pass-Filter-basics-and-types.html

here is simulation, can someone guess or explain, why there is such a big peak at resonant frequency (all pass filter has flat gain response)? is it because of quality factor of filter (Q) ?



Thanks!
 

Offline Benta

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Re: All pass filter simulation question
« Reply #1 on: June 12, 2021, 05:33:44 pm »
Because of R3 and R4. What on earth are they doing in your filter?

 

Offline lokajaudioTopic starter

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  • Posts: 7
  • Country: sk
Re: All pass filter simulation question
« Reply #2 on: June 12, 2021, 07:17:49 pm »
So + of the amp should be grounded right?..
 

Offline Benta

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Re: All pass filter simulation question
« Reply #3 on: June 12, 2021, 07:33:25 pm »
Yup. Just remove R3. You can choose R4=R2 to balance DC bias/offset for the amp.
 


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