[sdiy] Happenin' new opamp

[Rutger Vlek]

Interesting to hear what everyone's favourites are. I also selected the
OPA1679 recently for new designs (audio), but still wondering which opamp
to use (or keep using) with respect to CV/DC stuff. I'd like to improve
upon the offset and drift I've seen with the TL074, and rail-to-rail would
be awesome as I've seen situations where Eurorack audio-rate-CVs at high
frequencies really suffer. Any other suggestions for a good
price-quality-ratio part for CV paths?

Rutger

2018-04-19 19:28 GMT+02:00 Oren Leavitt <obl64 at ix.netcom.com>:

> Thanks for the info on OPA1678/9! I do still find myself using the LT1013
> a lot for CV/DC stuff (where the slow slew rate isn't an issue).
>
>
>
> On 4/19/18 11:16 AM, Tim Ressel wrote:
>
>> I pretty much use just 2 amps now; the 1678/9 any time I need
>> performance, and the TL082/4 for generic stuff. My new filter module is a
>> good example: 1678 for the audio processing and a TL082 for CV processing.
>>
>> In a way it feels funny to reduce the huge universe of op amps down to 2
>> parts. I know there are many applications where other amps are better. High
>> power, high voltage, high accuracy, high frequency, etc. But for what I
>> tend to do these two pretty much cover it. Many thanks for the dudes who
>> came up with it!
>>
>> --Tim (parts nerd) Ressel
>>
>>
>> On 4/19/2018 8:15 AM, Steve Lenham wrote:
>>
>>> I too designed the 1678 into a new product after Tim's original post
>>> drew it to my attention, and they work very nicely.
>>>
>>> The power of networking, eh - wonder if it will catch on?
>>>
>>> Cheers,
>>>
>>> Steve L.
>>> Benden Sound Technology
>>>
>>>
>>> On 19/04/2018 15:40, Matthias Herrmann wrote:
>>>
>>>> Nice.
>>>> I use the OPA1678 as my new working horse for quite a while now.
>>>>
>>>>     *From: *Synth-diy <synth-diy-bounces at synth-diy.org
>>>>     <mailto:synth-diy-bounces at synth-diy.org>> on behalf of Mattias
>>>>     Rickardsson <mr at analogue.org <mailto:mr at analogue.org>>
>>>>     *Date: *Thursday, 19 April 2018 at 14:16
>>>>     *To: *Tim Ressel <timr at circuitabbey.com <mailto:
>>>> timr at circuitabbey.com>>
>>>>     *Cc: *Synth DIY <synth-diy at synth-diy.org
>>>>     <mailto:synth-diy at synth-diy.org>>
>>>>     *Subject: *Re: [sdiy] Happenin' new opamp
>>>>
>>>>     I'm throwing in some news (for me at least) about the fairly new
>>>>     OPA1678/79 low-noise rail-to-railFET-input op-amps that I was trying
>>>>     as substitutes for the OPA1652/54, which has a price more than twice
>>>>     as high. The specifications are remarkably similar, and by accident
>>>>     I got in contact with TI's John Caldwell. He writes:
>>>>
>>>>     "I’ll let you in a on a little secret, the silicon is identical
>>>>     between the two devices. OPA1652 was released by another engineer
>>>>     before me, and when I took over the portfolio of audio op amps I
>>>>     personally felt that OPA1652 was too expensive to address the bulk
>>>>     of audio opportunities. For that reason, we made some changes to the
>>>>     production testing (used new test hardware that let us test more
>>>>     units faster) to reduce the manufacturing cost and re-released the
>>>>     device at a lower price point.
>>>>     Fun fact: the OPA1652 / OPA1678 has the lowest broadband voltage
>>>>     noise of any FET-type input amplifier in TI’s portfolio. It even has
>>>>     lower broadband voltage noise than the much more expensive OPA827."
>>>>
>>>>     I don't know if this was known before, but anyway great to have the
>>>>     same brilliant chip for a fraction of the price... and isn't it a
>>>>     great attitude about quality product sales? :-)
>>>>
>>>>     Regarding the inputs, which they don't mention being FET in the
>>>>     OPA1678 datasheet:
>>>>
>>>>     "We received your feedback on the OPA1678 datasheet. With regards to
>>>>     mentioning the input device type, the OPA1678 is fabricated on a
>>>>     CMOS process, so yes the device type is indeed a FET (MOSFET). This
>>>>     is also shown in the simplified diagram of the internal architecture
>>>>     on the first page.
>>>>     Calling it a “FET” input sometimes raises confusion between whether
>>>>     or not the devices is JFET or CMOS and I wanted to avoid that when I
>>>>     wrote the OPA1678 datasheet."
>>>>
>>>>     /mr
>>>>
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>>
>>
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