LM13600 vs CA3280 vs ???? [was]Re: [sdiy] linearize OTA for VCF?

[Jim Patchell]

jhaible at t-online.de wrote:

> Maybe the 3280 just has better transistors? (Lower noise,
> lower offset?) How much SNR improovement is there in the
> 3280 (I mean 3280 with diodes vs. 3280 without diodes ?)
> More than 10dB?
>
> JH.

    Here are some of my thoughts about integrated OTA's, and I have used
a fair number of them.  I have built OTA's out of CA3096's (back in the
dark ages you would say), I have used CA3080's, CA3280's, and a
smattering of LM13600/700's.  When the CA3280's first came out, they
were so much better than anything else, I have pretty much made this the
OTA of choice when I need an OTA.  One of the things that really
atrracted me to the CA3280 was the low control feedthough.  The other,
was low noise.

    This does not say the others are of no use.  The LM13700 is very low
cost (about 4 times cheaper than the CA3280).  Also, because of the fact
that the diodes have nothing else hooked to them in the linearizing
network, I can do things with them I cannot do with the CA3280.

    Now the CA3080 is one part I have not purchased for a long time, in
fact, I am still using the ones I got a long time ago.  In fact, the
ones I have are so old they are in TO-99 cans.

    I no longer use the CA3096 either, although, I do the same thing now
with the THAT140 (which seems to make very nice OTA's).  I have used the
THAT140 to make an OTA based triangle oscilator and a 4 pole LPF.

    Overall, though, I still have not found anything to beat the
CA3280...and of course, that makes me quite nervous because you can only
get them from Intersil, afaik.

    -Jim