[sdiy] Using both OTAs in 13700 as one OTA

[Mattias Rickardsson]

Simon,

what about the temperature dependencies in the transistor case?
Is that control circuit more sensitive for temperature variations?

/mr


On 10 February 2016 at 09:08, Simon Brouwer <simon.o at brousant.nl> wrote:
> 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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