PDM Filters

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PDM Filters

Postby frank carcia » Tue Feb 11, 2003 12:27 pm

Hi All,
I just ran my filter on Micro Cap. There is 7 dB of peaking at 3 ohm
load and 3 dB of peaking at 2 ohm load. At 1 ohm load the response is very flat out to about 10 KHz. Thinking back I increased the cap values
a bit from the design in the book reducing the output Z. It would be best to scale your filter based on mine with 1 ohm load. The switching frequency attenuation was about 75 dB so my measured value of 70
appears accurate. I will bring print outs with me Saturday if anyone wants to see them. Anybody wanting a free copy of this program. Search on Micro Cap. You can down load a student copy free which should do this job
OK fine. 3.5 meg file zipped. When I increase power, my filter should be perfect. Time to fire up the other final. I guess I was thinking ahead when
I picked my values back in '96. At 3, 2, 1 ohm load the attenuation was a straight slope out to 150 KHz for 100 dB of attenuation. Again the filter tested is 32 UH in 20 UF to ground 24 UH to output and 8 UF across output.

WA1GFZ
frank carcia
Senior Contributer
 
Posts: 765
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Location: Enfield Ct. / Niantic Ct.

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