[sdiy] Combining currents from different OTA outputs

[Tim Parkhurst]

On Sat, May 23, 2009 at 8:04 PM, Aaron Lanterman
<lanterma at ece.gatech.edu> wrote:
>
>
> I'm guessing SSM2164s will also play nice like this (although in what I'm
> working on now I'm relying on the tanh nonlinearity of OTAs).
>
> Come to think of it... although this is sort of a new topic... what kind of
> distortion characteristics do the SSM2164 have if you start pushing them to
> the limit? Just curious in case anyone had tried it.
>
> - Aaron

Hi Aaron,

Since the 2164 is a current output device, it should work like you've
described without any problems. The disadvantage to the 2164 is that
it is not a differential input device (it sounds like your scenario C
may need diff inputs). The advantage to the 2164 is that it's
relatively cheap ($3.50 for four VCAs) and has very wide dynamic range
(100dB attenuation, 20dB gain, so you can get 120dB if using it purely
as a VCA).

I've pushed the 2164s in the Mankato pretty hard, but I don't usually
hear mine break up or distort. I'm sure they do eventually. Maybe I
need to build a few more VCOs to get enough signal level going ;-)
Anyone else care to chime in on this one?

Tim (2164 fanboy) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings