SV: RE: [sdiy] PAIA VCO, LM13700 diode temp comp.

[harrybissell]

Woah. With that load of components I'd buy Q81 resistors and be done
with it.  I can see using the active circuits (Dial-a-tempco etc) if you want to
compensate out ALL the oscillator errors.  I don't have the oven that it would
take to research drifts that small.   It takes a lot of PCB real estate as well...

H^) harry

karl dalen wrote:

> Thanks for that diy report Phillip, most valuable!
>
> KD
>
> --- phillip m gallo <philgallo at attglobal.net> skrev:
>
> > Karl,
> >
> > After decades of staring at the National "app note" and wondering what it's
> > result would be, PAIA's publishing of their VCO implementation based upon
> > the technique finally caused me to break down and try the approach.
> >
> > I built a pair of VCO's based upon the PAIA scheme for the sawtooth core
> > (but used different wave shapers).  As Jim points out the Gm of the OTA is
> > what temp. compensates the core.  My variance from the PAIA implementation
> > was;
> >
> > 1)using a REF-02 for expo, comparator and waveshaper references.
> > 2)used MAT-03's for the expo pair,
> > 3)used an AD823 for the integrator buffer on one VCO and a LF412 for the
> > alternate.
> > 4)implemented a POT for the Hi-Fz tracking adjustment.
> > 5)"leveled" the MAT03's to the height of the socketed '13700 so they could
> > share a piece of aluminum as a common radiator.
> > 6)As is my general practice i used 1% and 2% film resistors (for what that's
> > worth).
> >
> > I implemented the VCO's on perf board so i could wire separate ground star
> > networks for the AC and DC circuit components (meeting at supply input).
> > Given the parts, you can build the core in an evening to analyze your
> > impression of the circuit.
> >
> > I was quite pleased and testing exhibited better results than that reported
> > by Ian but one set of test i didn't do was swap a variety of '13700's into
> > place to note their effect.  Both VCO's did perform similarly.  The VCO's
> > and notes from testing are still in storage although i moved nearly a year
> > ago (those who've visited my garage understand).  I'll be digging the VCO's
> > out of storage for project reasons in a few weeks and re-run the tests if
> > you're interested.
> >
> > regards,
> > p
> >
> > -----Original Message-----
> > From: owner-synth-diy at dropmix.xs4all.nl
> > [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of karl dalen
> > Sent: Monday, October 17, 2005 4:42 PM
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: [sdiy] PAIA VCO, LM13700 diode temp comp.
> >
> >
> > Long time ago there was discussions on the PAIA
> > VCO temp drift compensation using the diodes of
> > the LM13700, how did that turned out?
> >
> > Was it a good idea of temp compensation?
> >
> > REG
> > KD
> >
> >
> > --
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> >
> >