[sdiy] CMOS CD4046 ring mod??

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At 2:05 PM +0000 12/27/01, Scott Gravenhorst wrote:
>harry <harrybissell at prodigy.net> wrote:
>>Hmmm... as I recall former synth-diy "bad boy" Bjorn Julin used the 4046
>>phase comparator I  (ex-or gate) as a ring modulator in his 4046 VCO that
>>also featured a sawtooth output. Using the ex-or gate as a ring mod might
>>not have been the most clever feature of the design (the sawtooth out is,
>>IMHO)...

I'd like to see that.

>>but making the unused phase comparator a ring mod is pretty cool.

I'm basing the possibility solely on it's description.  The application
notes I have show a block diagram, but no schematics.  So "Phase Comparator
II" is still a black box.

>Yep, this is the one that I mentioned...  I could never
>get any serious range out of the VCO part, so I never
>finished making a VCO out of it.  If anybody can claim
>better than 2.5 octaves of linear range, I'd love to
>see how they did it.

Of course, it has a VCO, but as far as I tell tell, it isn't linear over a
wide range.  As part of a PLL it doesn't have to be.

>I'm thinking of trying an external linear V-I current sink
>out of pin 12 to try to linearize it over a wider CV range,
>but no round-tuit yet.  His technique for making saw would
>still be useful for using the device as a PLL though.

OK :)