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Resonance below 0.707 results in errors/instabilities
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August 19, 2017 - 6:17 pm
Member Since: August 7, 2017
Forum Posts: 5
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Hey there,

I noticed that, while designing the resonant LPF, the frequency response always went to "infinity" when the values for Q went below a certain point, maybe around 0.7. Any idea why this is or how to fix this?

Thanks

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August 21, 2017 - 8:26 am
Member Since: January 29, 2017
Forum Posts: 693
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Use the sample project from Chapter 6 (the 2nd order resonant LPF). There is no issue with Q below 0.707 -- I've taken it all the way down to Q = 0.01 with no problems. The intermediate variable d = 1/Q will fail if Q = 0.0, but you can take the value down pretty close to zero. 

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Are you working on some other resonant LPF? If not, check your updating equations against the book code.

- Will

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