https://www.ti.com/lit/ds/symlink/jfe2140.pdf

Even more interesting if you put the two fets in parallel.

Am 02.06.23 um 19:34 schrieb John Larkin:
>
> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>
> Even more interesting if you put the two fets in parallel.

I prefer On Semi CPH3910. I paralleled 16 of them.
More bang (less voltage noise) per buck.

< https://www.flickr.com/photos/137684711@N07/52420371063/in/datetaken/
>

<
https://www.diyaudio.com/community/threads/ultra-low-noise-jfets-from-texas-instruments.375079/page-12#post-7364203
>

Gerhard

On Friday, June 2, 2023 at 1:35:13 PM UTC-4, John Larkin wrote:
> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>
> Even more interesting if you put the two fets in parallel.

Those are mainly for the numerous differential amplifier applications for JFETs.

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
>
> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>
> Even more interesting if you put the two fets in parallel.
>
>

Encouraging that they’re bringing it out in 2023. The matching is very
good, and the 1/f corner is excellent.

Wiring them in parallel basically gets you a $3 CPH3910, only slower.

I’m not sure that I believe 1 nV noise with only 10 mS gM

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
>>
>> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>
>> Even more interesting if you put the two fets in parallel.
>>
>>
>
> Encouraging that they’re bringing it out in 2023. The matching is very
> good, and the 1/f corner is excellent.
>
> Wiring them in parallel basically gets you a $3 CPH3910, only slower.
>
> I’m not sure that I believe 1 nV noise with only 10 mS gM
>
> Cheers
>
> Phil Hobbs
>

It might be interesting to run a couple of packages in parallel, to get
lower noise while keeping the good matching. That would avoid having to
use op amp bandaids on discrete pairs to get decent DC performance, which
we have to do sometimes.

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

On 6/2/2023 1:34 PM, John Larkin wrote:
>
> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>
> Even more interesting if you put the two fets in parallel.
>

What does it mean for a product to be a "Burr-Brown" at this point? It's
unclear to me from the document if this is an actual new product, or a
re-released old product, or if "Burr Brown" is just like a trim-line
marketing moniker at this point, like buying a Chrysler New Yorker with
the "Mark Cross package."

On Fri, 2 Jun 2023 19:15:41 -0400, bitrex <user@example.net> wrote:

>On 6/2/2023 1:34 PM, John Larkin wrote:
>>
>> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>
>> Even more interesting if you put the two fets in parallel.
>>
>
>
>What does it mean for a product to be a "Burr-Brown" at this point? It's
>unclear to me from the document if this is an actual new product, or a
>re-released old product, or if "Burr Brown" is just like a trim-line
>marketing moniker at this point, like buying a Chrysler New Yorker with
>the "Mark Cross package."

TI acquired b-b in 2000. Some parts are still considered to be in the
b-b division, but I don't know if that has a physical meaning. It may
just be a trademark now, mostly for audio parts.

I asked TI for support on a different part, and the guy said "That's a
Burr-Brown part, we don't know much about it."

On Fri, 2 Jun 2023 23:09:18 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
>>>
>>> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>>
>>> Even more interesting if you put the two fets in parallel.
>>>
>>>
>>
>> Encouraging that they’re bringing it out in 2023. The matching is very
>> good, and the 1/f corner is excellent.
>>
>> Wiring them in parallel basically gets you a $3 CPH3910, only slower.
>>
>> I’m not sure that I believe 1 nV noise with only 10 mS gM
>>
>> Cheers
>>
>> Phil Hobbs
>>
>
>It might be interesting to run a couple of packages in parallel, to get
>lower noise while keeping the good matching. That would avoid having to
>use op amp bandaids on discrete pairs to get decent DC performance, which
>we have to do sometimes.

Yes, diff pairs in parallel would be good too, if you really need
diff.

I like the clamp diodes; I might use it just for them.

There's probably some dumb CMOS part that accidentally has pA or fA
clamp diodes. I've used a DG408 analog mux just as an 8-channel rail
clamp.

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
> On Fri, 2 Jun 2023 23:09:18 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
>>>>
>>>> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>>>
>>>> Even more interesting if you put the two fets in parallel.
>>>>
>>>>
>>>
>>> Encouraging that they’re bringing it out in 2023. The matching is very
>>> good, and the 1/f corner is excellent.
>>>
>>> Wiring them in parallel basically gets you a $3 CPH3910, only slower.
>>>
>>> I’m not sure that I believe 1 nV noise with only 10 mS gM.
>>>
>>
>> It might be interesting to run a couple of packages in parallel, to get
>> lower noise while keeping the good matching. That would avoid having to
>> use op amp bandaids on discrete pairs to get decent DC performance, which
>> we have to do sometimes.
>
> Yes, diff pairs in parallel would be good too, if you really need
> diff.

Not much point otherwise, unless the somewhat-better 1/f corner is a big
deal in a given application. CPH3910s are quieter in the flatband, at
1/10 the price.

The low noise at indifferent gM is interesting, though. An ideal BJT’s
noise temperature is Tj/2, compared to 2/3 Tj for an ideal JFET.

An ideal BJT at 0.25 mA Ic has a gM near 10 mS, so its-Hz voltage noise is
ideally

sqrt(0.5 * 4kT/gM), about 0.9 nV.

An ideal JFET with the same gM has sqrt(1.5)
times more, about 1.1 nV, which is close to what TI claims.

However, that doesn’t leave much space for the resistance of the silicon
and wiring. So using a few packages in parallel makes some sense.

>
> I like the clamp diodes; I might use it just for them.
>
> There's probably some dumb CMOS part that accidentally has pA or fA
> clamp diodes. I've used a DG408 analog mux just as an 8-channel rail
> clamp.

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

On 2023-06-02 19:24, John Larkin wrote:
> On Fri, 2 Jun 2023 19:15:41 -0400, bitrex <user@example.net> wrote:
>
>> On 6/2/2023 1:34 PM, John Larkin wrote:
>>>
>>> https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>>
>>> Even more interesting if you put the two fets in parallel.
>>>
>>
>>
>> What does it mean for a product to be a "Burr-Brown" at this point? It's
>> unclear to me from the document if this is an actual new product, or a
>> re-released old product, or if "Burr Brown" is just like a trim-line
>> marketing moniker at this point, like buying a Chrysler New Yorker with
>> the "Mark Cross package."
>
> TI acquired b-b in 2000. Some parts are still considered to be in the
> b-b division, but I don't know if that has a physical meaning. It may
> just be a trademark now, mostly for audio parts.
>
> I asked TI for support on a different part, and the guy said "That's a
> Burr-Brown part, we don't know much about it."
>

It sounds as though they pulled something out of the BB files and
re-implemented it on a modern process with good JFETs.

Pretty cool, in 2023.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On a sunny day (Fri, 02 Jun 2023 10:34:58 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<5u9k7ih15isssggnooi5rjqp246snh9lek@4ax.com>:

>
>https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>
>Even more interesting if you put the two fets in parallel.

It seems a bit strange to me
In cases where I wanted to use a JFET I would _not_ like diodes on the gate
(extra capacitance, C variable with voltage too), and most certainly not a reverse diode capacitance
path from the supply line to the gate.
OK it seems to be for the audiophile market (XLR connector and < 100kHz link)
I used JFETS at much higher frequency.
As to the many dB signal to noise for audio, some hysteria
who seriously has a place to listen to music or whatever that is silent enough!
Nowhere here, and not in nature either.
In fact for some transmissions I did in the long ago past use a compander
so you could actually hear people speaking softly at the receiver end, or the not so load parts of music.
So maybe the audiophiles club will like it. They have $$$$ to sacrifice...
For me it a big joke that chip.

On Sun, 04 Jun 2023 09:20:24 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Fri, 02 Jun 2023 10:34:58 -0700) it happened John Larkin
><jlarkin@highlandSNIPMEtechnology.com> wrote in
><5u9k7ih15isssggnooi5rjqp246snh9lek@4ax.com>:
>
>>
>>https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>
>>Even more interesting if you put the two fets in parallel.
>
>
>It seems a bit strange to me
>In cases where I wanted to use a JFET I would _not_ like diodes on the gate
>(extra capacitance, C variable with voltage too), and most certainly not a reverse diode capacitance
>path from the supply line to the gate.
>OK it seems to be for the audiophile market (XLR connector and < 100kHz link)
>I used JFETS at much higher frequency.
>As to the many dB signal to noise for audio, some hysteria
>who seriously has a place to listen to music or whatever that is silent enough!
>Nowhere here, and not in nature either.
>In fact for some transmissions I did in the long ago past use a compander
>so you could actually hear people speaking softly at the receiver end, or the not so load parts of music.
>So maybe the audiophiles club will like it. They have $$$$ to sacrifice...
>For me it a big joke that chip.

This is too good a part for audio.

As the front end of a super-quiet amp, the protective diodes are
handy.

On a sunny day (Sun, 04 Jun 2023 03:26:04 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<8hpo7il7l80du1r4c2i4tja5v1580dektj@4ax.com>:

>On Sun, 04 Jun 2023 09:20:24 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Fri, 02 Jun 2023 10:34:58 -0700) it happened John Larkin
>><jlarkin@highlandSNIPMEtechnology.com> wrote in
>><5u9k7ih15isssggnooi5rjqp246snh9lek@4ax.com>:
>>
>>>
>>>https://www.ti.com/lit/ds/symlink/jfe2140.pdf
>>>
>>>Even more interesting if you put the two fets in parallel.
>>
>>
>>It seems a bit strange to me
>>In cases where I wanted to use a JFET I would _not_ like diodes on the gate
>>(extra capacitance, C variable with voltage too), and most certainly not a reverse diode capacitance
>>path from the supply line to the gate.
>>OK it seems to be for the audiophile market (XLR connector and < 100kHz link)
>>I used JFETS at much higher frequency.
>>As to the many dB signal to noise for audio, some hysteria
>>who seriously has a place to listen to music or whatever that is silent enough!
>>Nowhere here, and not in nature either.
>>In fact for some transmissions I did in the long ago past use a compander
>>so you could actually hear people speaking softly at the receiver end, or the not so load parts of music.
>>So maybe the audiophiles club will like it. They have $$$$ to sacrifice...
>>For me it a big joke that chip.
>
>This is too good a part for audio.
>
>As the front end of a super-quiet amp, the protective diodes are
>handy.

Any spike on the supply will feed to the input via the capacitance of the protection diode on the supply side.
For RF you do _not_ want varicaps (that is what they do if input bias changes) on the input.
You could argue that if voltage goes up one diode gets less capacitance and the other more.... and vice versa,
would have to measure it.
Maybe someone knows how much thermal? noise those diodes create when receiving alien signals...
Made some nice RF frontend with a JFET cascode long ago.
JFETs make nice LC and xtal oscillators too.
circuit examples:
https://www.ti.com/lit/an/snoa620/snoa620.pdf