[sdiy] Happenin' new opamp

Oren Leavitt obl64 at ix.netcom.com
Thu Apr 19 19:28:15 CEST 2018


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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