I'm in need of help to create a notch filter badly. I have tried and given up many times.
I have tried the twin t, an lmf100 max7410 ICs and a bainter notch filter.
The bainter I used an online calculator with no luck at all.
The twin T(active), I could not tune it for a deep enough notch.
The lmf100 and max7410 ICs I could not get enough attenuation and I also don't like the low voltage supply limit(low in/out input signal to deal with).
can anyone help me with any of these or any other designs? I have many opamps btw. I would like to know anyone's success and if I can get help with equations for the bainter notch maybe?
I want at least 70db or more of attenuation and the input will be a sine wave of 50hz and 1khz and the q depends but it needs to be enough to allow 3rd harmonics un touched. As you can guess it is for a distortion detector.
I have tried the twin t, an lmf100 max7410 ICs and a bainter notch filter.
The bainter I used an online calculator with no luck at all.
The twin T(active), I could not tune it for a deep enough notch.
The lmf100 and max7410 ICs I could not get enough attenuation and I also don't like the low voltage supply limit(low in/out input signal to deal with).
can anyone help me with any of these or any other designs? I have many opamps btw. I would like to know anyone's success and if I can get help with equations for the bainter notch maybe?
I want at least 70db or more of attenuation and the input will be a sine wave of 50hz and 1khz and the q depends but it needs to be enough to allow 3rd harmonics un touched. As you can guess it is for a distortion detector.
Post your schematics; maybe there is some obvious mistake, since all of these filters can be made to work properly.
You can base yourself on the SVF- based notch of this THD meter:
http://www.diyaudio.com/forums/equipment-tools/207513-simplistic-distortion-meter.html
It is proven and tested. It is of the same family as the Bainter, meaning the rejection does not depend on the accuracy of components, but the quality of the capacitors is essential: you need PS or PP type, or as a second best ceramic COG or silver mica
You can base yourself on the SVF- based notch of this THD meter:
http://www.diyaudio.com/forums/equipment-tools/207513-simplistic-distortion-meter.html
It is proven and tested. It is of the same family as the Bainter, meaning the rejection does not depend on the accuracy of components, but the quality of the capacitors is essential: you need PS or PP type, or as a second best ceramic COG or silver mica
let me use the calculator again and re try. It was a long time ago that I tried.
by the way I really like the circuit you posted. I am going to try the bainter first using the calculator and I will post schematic and results etc
by the way I really like the circuit you posted. I am going to try the bainter first using the calculator and I will post schematic and results etc
Ok, update:
In reference to the Chang puak calculator the values I chose were:
Q=5
Null freq = 50hz
C1/2 470nF
R1/2 1k ohm
R3/4 620 ohm
R5/6 68k ohm
Real world results:
Notch freq = 51hz
Attenuation: 455mV input / 56mV output (horrible)
So, the notch calculation worked perfect essentially. But the attenuation is horrible. Any ideas? The original resistance values were different then the ones I chose for r3/4 and r5/6 because there were wacky values like 677.26 ohms for instance can this possibly be an issue? How can I get a deeper notch!
In reference to the Chang puak calculator the values I chose were:
Q=5
Null freq = 50hz
C1/2 470nF
R1/2 1k ohm
R3/4 620 ohm
R5/6 68k ohm
Real world results:
Notch freq = 51hz
Attenuation: 455mV input / 56mV output (horrible)
So, the notch calculation worked perfect essentially. But the attenuation is horrible. Any ideas? The original resistance values were different then the ones I chose for r3/4 and r5/6 because there were wacky values like 677.26 ohms for instance can this possibly be an issue? How can I get a deeper notch!
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