Substrate temperature stabilized

[Rick Jansen]

Haible_Juergen wrote:

> > (I believe that the transistors [in a MAT-04] are "better" than 
> > in a 3086, but I thought 3086 transistors were good enough, when 
> > the temperature effects would be cancelled.)

Opinions on this seem to vary a lot, so the only way to really find 
out is to actually build the circuits I guess.  At least the MAT-04
offers a technical possibility to reach the quality level of the uA726
at comparable cost. The temperature control circuitry isn't cheap,
the LM329 costs ca US$ 6,-, but we're only building a few, not thousands
I guess. The drawback of course is that the MAT-04 is only made by
PMI, which has just been taken over by Analog Devices(?), so there's
a chance the availability is not guaranteed in years to come. The LM3046 
is extremely common, and second- and maybe even triple-sourced.

The Old Crow wrote:

>   According to National Semiconductor specs and appnotes, the LM3046
> (LM3086), when used in a feedback temperature stabilized circuit, has an
> exponential conformity of 0.25% from 20Hz to 15KHz, which is just fine as
> far as I'm concerned.  
                      
You have a point there of course. At lower frequencies the exp conformity
is much better than 0.25%, and I guess most of us won't use VCO's above
a few kHz, or do we have bats on the list? 

I'm now leaning again towards a 3046-based circuit:

Part            Pro                                   Con
-------------   ----------------------------------    --------------------
LM3046/CA3046   cheap                                 Less log conformant
                Available
                Substrate temperature controllable

MAT-02/LM394    Excellent characteristics             External temp control
                Available                             Price? (ca. US$ 20,-)

MAT-04          Excellent characteristics             No 2nd source
                Available                             Price? (ca. US$ 20,-)
                Substrate temperature controllable

uA727           Excellent characteristics             Unavailable
                Substrate temperature controlled

So, I'll go for the 3046 and try a MAT-04 as another experiment.

Rick Jansen
__
rick at sara.nl   http://www.sara.nl/Rick.Jansen
_____________________________________________
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