Descret OTA was "that Japanese site"

[terry michaels]

Message text written by "tomg"
>
> From what I know this is the gm stage of the famous SSM2044.  

I have seen it before. I know I have but I don't remember what it was
called. I went through my books and can't find it. Somebody help...it
is hurting my head.

> The diode should be replaced by another 2N3906 connected as a diode. This
> forms a current mirror, and the transistors should be matched. (A 1N4148
> and a 2N3906 won't have the same Vbe.)

Cool! I'll try it.
 
> >I built a VCA out of it and works just like you think it would.....

> Perhaps one could build this circuit with SMDs on a tiny PCB to plug them
> into a 8 pin DIP to replace the CA3080 in existing circuits.

Seems like a lot of work...unless of course it worked better than 3080s. I
just thought it might be a better vca....only kidding about not needing
600/700s.

I tried a few more things with it....whatever "it" is it's fun to play
with.
-tg
<

Hi Tom:

This circuit is not new, it was used by ARP in their 4019 VCA module and
their 4014 Balanced Modulator module around 1970.

You must be careful if you want to replace the CA3080 with this, because
the output voltage swing is very limited, only about 0.5 volts below ground
potential.  IMO the only proper way to use this circuit is to run the
output directly into the summing node of an op-amp set up as an invertor.

Terry Michaels