[sdiy] Using both OTAs in 13700 as one OTA

[Simon Brouwer]

Yes it was.
 
However, this circuit still uses one opamp, a resistor and at least two diodes.
The more straightforward approach adds two resistors, and replaces one diode by
a
transistor.
So this doesn't add much in complexity and cost, and you can control both halves
of an LM13700 independently.
 
Best regards
Simon
 

> Op 9 februari 2016 om 20:20 schreef Mattias Rickardsson <mr at analogue.org>:
>
>
> Aha!
> It *was* a beautiful trick. :-)
>
> http://electronotes.netfirms.com/AN399.pdf
>
> /mr
>
>
> On 8 February 2016 at 19:09, Ian Fritz <ijfritz at comcast.net> wrote:
> > The reference to the original Jung article is JAES, 23, 1975. This method
> > was widely used in EN projects. I looked at using this method with the
> > LM13700 to aid people who want to build off of these projects, but who can't
> > obtain the CA3080. It's also an easy way to improve S/N by 3dB, as pointed
> > out by Serge T. in his EN article from when the chip was new.
> >
> > I couldn't wade through Aaron's article either. It sounded like negating
> > then subtracting? Isn't that the same as adding?
> >
> > Ian
> >
> >
> >
> > On 2/8/2016 2:41 AM, Mattias Rickardsson wrote:
> >>
> >> On 4 February 2016 at 05:52, <ijfritz at comcast.net> wrote:
> >>>
> >>> Good grief! Just connect them directly in parallel. An example,
> >>> complete
> >>> with the W. Jung trick:
> >>>
> >>> http://electro-music.com/forum/viewtopic.php?highlight=jung+ota&t=50884
> >>
> >>
> >> What does it do? What is the "trick"?
> >> I feel like one of the answers in that thread:
> >> "I hadn't heard of this trick before, is there an article somewhere
> >> that explains the benefit of drawing bias current from V-? I feel like
> >> there's something obvious that I'm missing."
> >>
> >> I spontaneously found Aaron's idea potentially better than nothing,
> >> but I haven't plunged into it.
> >>
> >> /mr
> >>
> >
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