[sdiy] Temperature stable lin-exp converter with a CA3086 or CA3046

[Tim Ressel]

Roman,

The design only heats up the internal die of the part
in question: CA3046 or MAT04. The temperature is not
that great (40C). I use styrofoam arounf the IC to
insulate it, increasing stability and further
protecting outlying circuits.

As for the method of using a tempco: the curves of
tempco R's and diodes are not an exact match. So over
temperature you'll still get drift. With the heater
design, its stable across its entire temp design
range.

--TR

--- Sowa Roman <Roman.Sowa at upc.com.pl> wrote:
> I would avoid any designs that make heat on purpose.
> It's better
> to compensate IMHO than to heet up.
> Heat will spoil other circuits performance, degrade
> electro-caps
> as we'we learned recently from this list, and will
> make you buy
> bigger and bigger power supplies when your modular
> grow.
> 
> Roman
> 
> __-----Original Message-----
> __From: Rob Mantel [mailto:rob at arachnoids.org]
> __Sent: Monday, May 27, 2002 5:04 AM
> __To: SynthDIYmailinglist
> __Subject: [sdiy] Temperature stable lin-exp
> converter with a 
> __CA3086 or CA3046
> __
> __
> __Hi all,
> __
> __In this book I have here, they use a CA3086 (or
> CA3046) to 
> __build a lin-exp
> __convertor for a VCO. Two of the transistors inside
> do the real lin-exp
> __conversion, two others are used to control the
> temperature, 
> __one as 'sensor',
> __one as 'heater'. From what I understand of it this
> should 
> __lead to a constant
> __temperature of the ca3086 (kind of like the old
> ua726 got its constant
> __temperature from its oven), so no external
> temperature compensation is
> __needed anymore.
> __
> __Is this a well known thing to do? If so, why
> doesn't everyone 
> __do it this
> __way, it is a very cheap solution, no expensive
> parts involved 
> __at all. Does
> __anyone have any experience with the temperature
> stability of 
> __VCO's built
> __this way?
> __
> __Rob (who floods the list with questions today,
> sorry)
> __
> __
> __
>
__---------------------------------------------------------
> __This message has been scanned for viruses by
> MIMESweeper.
> __
> __Wiadomosc zostala sprawdzona pod katem wirusow
> przez
> __oprogramowanie MIMESweeper.
> __
> 
> 
>
---------------------------------------------------------
> This message has been scanned for viruses by
> MIMESweeper.
> 
> Wiadomosc zostala sprawdzona pod katem wirusow przez
> oprogramowanie MIMESweeper.
> 


__________________________________________________
Do You Yahoo!?
Yahoo! - Official partner of 2002 FIFA World Cup
http://fifaworldcup.yahoo.com