[sdiy] Happenin' new opamp

[Steve Lenham]

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
>