[sdiy] Heads up on SSM2210

[Grant Richter]

> b) The PNP version (SSM2220P) is widely used for MOTM expo generators in the
> VCFs.

Just wondering about the best "bang for the buck".

If you look at the datasheet for the SSM2220 and the MAT03, the SSM2220 has
all the significant specs as the least expensive grade of MAT03. But
SSM2220s were about a third the cost of a MAT03 (maybe plastic vs. metal
case or temp range?).

So I wonder what makes them decide to label one die a MAT03 and one a
SSM2220. I kind of suspect the SSM2220 is just the fallout from the MAT03
line, labeled for AC use rather than DC.

Based on my experience, a MAT03, SSM2220 or Linear Systems LS358 all require
about the same amount of high frequency compensation for log deviation
(similarly low Rbe). I've built VCOs using all three, and they all tracked a
keyboard just fine.

I guess the improved spec must be initial Vbe matching? Does this affect
total temperature stability? I am still not clear on the significance of the
spec for initial Vbe matching. For example, they all spec 10 mv. as a max.
mismatch, but typical specs improve by price. What is the actual affect of
Vbe mismatch in a VCO application?

Any insight is appreciated. Thank you.