CA3046 exponential converter

[BJ]

Steve Varner wrote:
> 
> I guess not many people have built the 3046 VCO and thermostat as shown in
> Klein's book. The difference between this design and the AN-299 design is
> that the matching transistors and one other transistor are used in the
> standard VCO way, and the last two are used for temperature sensing and
> heating. There is no transistor used for the clamp. I'll try this design
> and let people know how it works.
> 
> SV
> 
> --------------------------------------
> Steve Varner wrote earlier:
> 
> > Barry Klein has a CA3046 exponential converter (fig.4-4, p.87) in his
> > "Electronic music circuits." This is the same as the ENS-76 VCO option
> > 1A found in the "Preferred Circuits Collection." These schematics show
> > temperature compensation using the 2k tempco.
> > Barry also has a CA3046 2-transistor thermostat circuit (Fig. 4-3, p.86)
> > using the remaining transistors on the array (Q4 and Q5). It seems very
> > simple. (I suppose you would then leave off the tempco resistor and
> > replace it with a regular resistor.)
> > Has anyone built this exact VCO setup? If it works well... godbye
> > matched pairs and tempcos for me. 3046's only cost about 35 cents.

> > Steve Varner
> > mailto:varner at k-online.com

I dont know about you other but the oven controlled expoconverter
works wery well, wery wery well i would say, one example is the
Moog Source, who happens to have a oven expo, a little clumsy
design but wer well working.Remembering the test i did again
with a mates source this winter.
Rock solid tuning for several ours.

There is one point in the design of a oven controlled LM3046 you 
have to be avare off, and thats the value of the cappacitor 
for the ovens comparator ,when the two comparing
voltages are wery close to each other the comparator switches on 
to compensate for the temp drif,if the capp is small in value the
switching may be at several kilo herz and can produce interference
if a bad PCB layout is made or the VCO becomes "jittery"!

This "may" in a bad PCB design be one of the oven designs drawbacks!
But only if one are a neurotic personality!!!

In some designs i use a fairly large capp to get a slower response
of the comparator.

BJ's
5 cent