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

[Rob Mantel]

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)