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

[harry]

The heated expo converter is OK and many folk do use it.... It is power
hungry and generates heat, which might make everything ELSE drift...
so a lot of folks prefer the tempco resistor.

The uA726 used an amazingly low amount of current to do the heating, because
the die was so small. The 3046 is huge by comparison... and might not work as
well.
It takes time to stabilize, and will servo up-down-up-down... while holding
temperature... which might (argueably) be audible...

H^) harry

Rob Mantel wrote:

> 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)

--
Jihad Terrorism Conspiracy New World Order
Revolution Black Helicopters Freedom of
Speech First Amendment Rights: Carnivore Bait
go ahead and READ my e-mail I have nothing to
hide... how about YOU ???