[sdiy] SUPER CA3280's

[Ian Fritz]

Hi all --

I've been looking at the CA3280's I just bought from Futurlec.  Since they 
were so inexpensive, I was afraid that they might be some kind of 
rejects.  I characterized 20 of them using the same VCA-like test circuit 
that I used to look at a batch of chips obtained from Mouser a while back.

It turns out that the Harris chips from Futurlec are way better than the 
previous Intersil chips from Mouser.  For the Harris batch, the variation 
of offset with Iabc is about the same as the noise level, i.e., ~2mV.  For 
the Intersil batch the variation is up to 10x larger, although selected 
devices perform well.  The CA3080's I hve measured are all over the map, 
with variations in the 30mV - 100mV range not uncommon.

I also looked at the output linearity vs. Iabc for a couple of  the new 
chips.  The nonlinearity between 0 and 0.5mA is in the 0.5% - 0.8% 
range.  This is quite good, as I have measured nonlinearities up to 10% for 
LM13600 devices.

No guarantees that you will gst devices from the same batch, but at these 
prices ($1.30) everyone should stock up.

   Ian