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3 OHM PDM FILTER

PostPosted: Tue Feb 25, 2003 4:23 pm
by frank carcia
Hi All,
I did some Micro Cap simulation and learned that 3 filter sections are required when you get above a couple ohms of final load Z. I picked 3
ohms because below that my present filter works with 2 sections.
Starting at the modulator the three inductor values are 48 UH, 32 UH and
24 UH at the final. The 3 cap values are 8 UF, 6 UF and 3 UF at the final.
The performance is 75 dB attenuation at 85 KHz. The roll off is a nice slope starting around 10 HKz. The student version of Micro Cap works very well. We only have a few licenses here at work so free is very
nice. It was pretty easy to use. I picked 1/10 ohm drive Z. I can saved
the set up if anyone needs values for different loads. fc