[sdiy] Matching across matched pairs for dual VCOs

[JH.]

>Suppose you were building two VCOs that you wanted to be able to track
>one another pretty well, say for yummy FM goodness.
>
>Would there be an advantage to using, say, something like a THAT chip
>that has _four_ matched NPNs, so that your two expo converters would
>be matched with each other and also stay at the same temp?

I don't expect any advantage. Offset is an issue within each pair - the 
absolute Vbe at a certain current is not.
So you don't need to match any "offset" between pair 1 and pair 2.

As for tracking, you have to trim this anyway, because of resistor 
tolerances.

If you share a Quad array for two VCOs, you risk interlocking.
I don't say you *will* get such problems, but you surely have another 
potential problem to take care to avoid.

JH.