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I am looking for thiese chips in my (sh.ty)third world country (Turkey)<br>
But never found yet<br>
HOSHUYAMA wrote:<br>
<blockquote type="cite" cite="mid40FD485E.5030104@muj.biglobe.ne.jp">
<pre wrap="">Hello Scott,
Scott Gravenhorst wrote:
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<pre wrap="">One comment inline.
HOSHUYAMA <a class="moz-txt-link-rfc2396E" href="mailto:houshu@muj.biglobe.ne.jp"><houshu@muj.biglobe.ne.jp></a> wrote:
</pre>
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<pre wrap="">If I have "matched" and "floating" FETs (MOSFETs), I'd try a 4-pole
VCF based on the LPF structure in the following schematic replacing
the OTA by a FET, and the opamp by a CMOS inverter.
<a class="moz-txt-link-freetext" href="http://www5b.biglobe.ne.jp/~houshu/synth/Vcf0210.GIF">http://www5b.biglobe.ne.jp/~houshu/synth/Vcf0210.GIF</a>
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<pre wrap="">
I saw this the other day and it's implication went whizzing right over my little
wooden head.
This technique (I assume as depicted in the LPF inset) looks like a H11F1(s) could
be used, or perhaps a 4007UB to make a SVF from 2 of these LPF blocks. (or am I
being terribly naive?) I will not claim to understand this structure. It is not in
Lancaster's Active-Filter Cookbook. I am not at all sure exactly where the summing
node is! It's almost is if there are two virtual grounds (which could explain the
low Vds possibility) because of the dual feedback configuration. My guess is that
the source of the MOSFET would connect to the capacitor/amplifier input node.
</pre>
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<pre wrap=""><!---->
Exactly.
If the M5222 is replaced by a VCR, and R10 and R12 have the same
value "R", the cutoff frequency of the structure, "fc" is
fc = 1 / { 2 * pi * C4 * ( R + 2*VCR ) }.
Sam Hoshuyama
Saitama, Japan
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