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RE: It's a high pass filter, not a low pass filter

I was talking about the AC voltage across the across the bypass capacitor (which is falling with increasing frequency). I was responding to your comment that this would have become 0Vac by the time the frequency reached 20Hz. I was remarking that it never becomes literally 0Vac, no matter how high the frequency. Rather, it will be dropping off at something like 20dB per decade.

Viewing the AC voltage across the bypass capacitor (as you were previously discussing) as "the signal," one is discussing a low-pass filter.

One can indeed also discuss things from the point of view of the signal that is passed through the capacitor, and indeed then, as far as this desired audio signal is concerned, one is now instead discussing a high-pass filter. Again, I would not quite agree with your statement that "to get out of the affects of a high pass filter you need to go a decade up in frequency from the corner frequency. At that point the attenuation and the phase shift has stopped." There is no frequency at which the attenuation has literally stopped. Rather, the attenuation becomes so tiny that it has, for all practical purposes, stopped. And so I would absolutely agree with the spirit of what you are saying.



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  • RE: It's a high pass filter, not a low pass filter - cpotl 06/13/2116:33:06 06/13/21 (1)
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