[sdiy] Happenin' new opamp

Rob Spencer rob at gmsn.co.uk
Thu Apr 19 15:44:20 CEST 2018


Good to know! Would you mind I if share this on the GMSN forum? 

 

Rob Spencer

07590 267835

 

From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Mattias Rickardsson <mr at analogue.org>
Date: Thursday, 19 April 2018 at 14:16
To: Tim Ressel <timr at circuitabbey.com>
Cc: Synth DIY <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-rail FET-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



On 4 June 2017 at 17:39, Tim Ressel <timr at circuitabbey.com> wrote:
>
> I started out with the LM4562. Very nice, but as you say, high cabbage factor. Then I went to the LME49723. Noise is higher but amp is cheaper. If you really want to break the bank, go with the AD797. Super low noise, super high price.
>
> --timbo
>
>
> On 6/4/2017 2:29 AM, John P Shea wrote:
>
> 4x the price:
>
> http://www.ti.com/lit/ds/symlink/lm4562.pdf
>
> DIP & SOIC
>
> Regards,
> JPS
>
> On Sun, 4 Jun 2017 at 12:21 pm, Tim Ressel <timr at circuitabbey.com> wrote:
>>
>> It seems to be a popular amp. Mouser got 2500 of the SOICs in and blew
>> through them in days. They have 7K on order. I think they will become my
>> go-to amp for audio stuff. I'd write TI and ask for the QFN package.
>>
>> --tim
>>
>>
>> On 5/24/2017 10:09 AM, paula at synth.net wrote:
>> > Tim,
>> >
>> >  hey that's neat, though I feel the reverse, s shame it's not in a
>> > smaller 3x3 QFN package. The VSSOP is close though.
>> >
>> >  Thanks for the heads up :)
>> >
>> > Paula
>> >
>> >
>> > On 2017-05-23 21:30, Tim Ressel wrote:
>> >> Hey,
>> >>
>> >> Writing to say the OPA1678 from TI is a pretty nice little amp. Low
>> >> noise, low distortion, low bias current, low cost. Is a dual; OPA1679
>> >> is a quad. SMT only, sad to say, but that be the times we live in.
>> >>
>> >> http://www.ti.com/lit/ds/symlink/opa1678.pdf
>> > _______________________________________________
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>> >
>>
>> --
>> --Tim Ressel
>> Circuit Abbey
>> timr at circuitabbey.com
>>
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>
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> -- 
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
>
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