[sdiy] Weird Serge Resonant Filter topology in upper bands

[Guy McCusker]

Isn’t Rod Elliott’s Fig 7 exactly what Don drew?


On Thu, 15 Dec 2022 at 03:42, Lanterman, Aaron D via Synth-diy <
synth-diy at synth-diy.org> wrote:

>
>
>
> On Dec 13, 2022, at 4:39 AM, René Schmitz <synth at schmitzbits.de> wrote:
>
> On 13.12.2022 10:22, René Schmitz wrote:
>
> <SergeEQ.png>
>
> But if you swap + and -, and tap at the -input, then it works like I'd
> expect.
>
> Now it starts to look familiar. The opamp forms a negative impedance
> converter.
>
> And of course one can as well tap at the + input. Forming a voltage
> divider between C2/R1 and the NIC reflected R4/C1 impedance.
>
> So I did find a filter that looks like Rene’s filter (which I’m going to
> call the Rene filter until I find out something else it should be called),
> namely Figure 7 here on one of Rod Elliott’s pages:
>
> https://sound-au.com/articles/negative-z.htm#s4
>
> Except Rod’s op amp inputs are flipped relative to Rene’s.
>
> Aaron Lanterman, Prof. of ECE, Georgia Tech
> My blog on Education and Innovation: https://edupocalypsenow.wordpress.com
> My blog on Electronics and Programming: https://lantertronics.blogspot.com
> My YouTube channel on Electronics and Programming:
> https://www.youtube.com/c/lantertronics
>
>
>
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