opa145

G

George Herold

Guest
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.
 
On 9/4/19 1:45 PM, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.
Click to expand...

That datasheet raises the hair on the back of my neck. The amount of
marketing specsmanship is even higher than usual, and there's no
discussion whatever about the rising noise characteristic. With a 5-MHz
GBW and a noise spectrum that rises starting at 10 kHz, there's a lot
more high end than there is low end.

The OPA140 looks much better behaved. (I like it a lot, myself.)

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 Wednesday, September 4, 2019 at 2:18:18 PM UTC-4, Phil Hobbs wrote:
On 9/4/19 1:45 PM, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.


That datasheet raises the hair on the back of my neck. The amount of
marketing specsmanship is even higher than usual, and there's no
discussion whatever about the rising noise characteristic. With a 5-MHz
GBW and a noise spectrum that rises starting at 10 kHz, there's a lot
more high end than there is low end.

The OPA140 looks much better behaved. (I like it a lot, myself.)
Click to expand...
The opa140 does look nice. In this case I'm replacing the EOL opamp in an old
photodiode TIA. If I put in an opamp with 'better' GBW, then I think I'll have
to change all the feed back cap values... so I'll give the opa145 a look-see.

Figure 39 seems to indicate that there is no noise hump out beyond 10 kHz..
but who knows.

George H.
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
Click to expand...
 
On 9/4/19 3:22 PM, George Herold wrote:
On Wednesday, September 4, 2019 at 2:18:18 PM UTC-4, Phil Hobbs wrote:
On 9/4/19 1:45 PM, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.


That datasheet raises the hair on the back of my neck. The amount of
marketing specsmanship is even higher than usual, and there's no
discussion whatever about the rising noise characteristic. With a 5-MHz
GBW and a noise spectrum that rises starting at 10 kHz, there's a lot
more high end than there is low end.

The OPA140 looks much better behaved. (I like it a lot, myself.)
The opa140 does look nice. In this case I'm replacing the EOL opamp in an old
photodiode TIA. If I put in an opamp with 'better' GBW, then I think I'll have
to change all the feed back cap values... so I'll give the opa145 a look-see.

Figure 39 seems to indicate that there is no noise hump out beyond 10 kHz..
but who knows.
Click to expand...

That's the one that put me on guard--they don't tell you what frequency
it's done at, but one gathers that it's 1 kHz or thereabouts. They are
most mousey-quiet about what happens at other frequencies. Unimpressive.


Cheers

Phil Hobbs

(Coming to you from beautiful San Miguel Island in the Azores)

--
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 Wednesday, September 4, 2019 at 4:21:09 PM UTC-4, Phil Hobbs wrote:
On 9/4/19 3:22 PM, George Herold wrote:
On Wednesday, September 4, 2019 at 2:18:18 PM UTC-4, Phil Hobbs wrote:
On 9/4/19 1:45 PM, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.


That datasheet raises the hair on the back of my neck. The amount of
marketing specsmanship is even higher than usual, and there's no
discussion whatever about the rising noise characteristic. With a 5-MHz
GBW and a noise spectrum that rises starting at 10 kHz, there's a lot
more high end than there is low end.

The OPA140 looks much better behaved. (I like it a lot, myself.)
The opa140 does look nice. In this case I'm replacing the EOL opamp in an old
photodiode TIA. If I put in an opamp with 'better' GBW, then I think I'll have
to change all the feed back cap values... so I'll give the opa145 a look-see.

Figure 39 seems to indicate that there is no noise hump out beyond 10 kHz..
but who knows.


That's the one that put me on guard--they don't tell you what frequency
it's done at, but one gathers that it's 1 kHz or thereabouts. They are
most mousey-quiet about what happens at other frequencies. Unimpressive.


Cheers

Phil Hobbs

(Coming to you from beautiful San Miguel Island in the Azores)
Huh, I'm not paid enough.
Click to expand...

So this is a bit of an aside, but I need a new gig*.
There's a local defense contractor with jobs...
I should talk with the people I know who work there,
(I'm going in with an attitude that I'll hate it...
not good (!),
but with the 'right boss' it could be OK.)
A small company would be better for me.

So as I'm walking around (beer in hand), thinking about tomorrow.
And I think, my last teachspin project should be a
Phil Hobbsian upgrade to the photodiode preamp...
Out with this crappy opa124 eol opamp.
It's a big area PD, (PIN-44D ?)
~100's pF C-diode at zero bias, ~1-2uA of photo current
(there is ~2-3 uses so the specs vary...say 0 to 1 mA :^)

I've done a driven shield, (bootstrap) with an opamp.
(can I do a dual opamp circuit to drive the back end of the
PD?)
So I was going to play with the 'cascode' input.

and then my 'linked in' profile?

George H.

*my boss wanted me to post here (on SED**) that teachspin
is looking to hire another 'phd level' physics person.
If anyone is interested,
https://www.teachspin.com/join-our-team

**cause I told him ~90% of my circuit fixes come from here.
Hey if/when I do land a new gig I'm figuring SED will still
'have my back' circuit-wise.. I would really like more
local wisdom, I'm mostly stuck near Buf. NY. (kids)
for another few years.


--
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
Click to expand...
 
George Herold wrote...
So this is a bit of an aside, but I need a new gig*.
Click to expand...

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?


--
Thanks,
- Win
 
On 9/5/19 5:36 PM, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Click to expand...
ISTR something about not being paid enough. I remember vividly having
three kids in college at the same time. ;)

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 Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.
Click to expand...

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.
 
On Thursday, September 5, 2019 at 5:58:56 PM UTC-4, Phil Hobbs wrote:
On 9/5/19 5:36 PM, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?


ISTR something about not being paid enough. I remember vividly having
three kids in college at the same time. ;)
Click to expand...
No TBH, the amount of money is not that important.
There is certainly a part in where the profits are being spent.

My boss (who works ~ for free and I'm not counting)
wants to hire a 3rd Phd. we'll have more phd's than
production people...!
it just seems crazy to me.
(If anything we need more production people.)

George H.


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
Click to expand...
 
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH
Click to expand...

I didn't have such a dilemma. I got fired.
 
On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Click to expand...
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH



--
Thanks,
- Win
Click to expand...
 
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.
Click to expand...

Being fired was great. Started my life over.
 
On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.
Click to expand...

Mine too.

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 Fri, 6 Sep 2019 15:11:33 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.


Mine too.

Cheers

Phil Hobbs
Click to expand...

I designed $200M worth of electronics for them, and then they fired me
for insubordination. The idiots didn't understand that engineers are
supposed to be insubordinate.
 
On 06/09/19 20:33, John Larkin wrote:
On Fri, 6 Sep 2019 15:11:33 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.


Mine too.

Cheers

Phil Hobbs

I designed $200M worth of electronics for them, and then they fired me
for insubordination. The idiots didn't understand that engineers are
supposed to be insubordinate.
Click to expand...

Of course. Human resources are fungible. (Aren't they?)

Whatever happened to the "personnel department"?
 
On Friday, September 6, 2019 at 3:11:40 PM UTC-4, Phil Hobbs wrote:
On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.


Mine too.
Click to expand...
Right, that's what it feels like.
I've always been a late bloomer so my mid life
crisis can be a bit late at 60. :^)

If you are not working for yourself,
then its's a matter of finding the right boss.
(who wants you.)

The worst part will be separation from my current
place of employment, I really hate conflict.

I've always wanted to be the 'lab guy' at some
college/ uni. which are 'liberal crazy*' these days,
and I sorta shudder at having to conform.

George H.

*crazy = authoritarian


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
Click to expand...
 
On Fri, 6 Sep 2019 20:46:38 +0100, Tom Gardner
<spamjunk@blueyonder.co.uk> wrote:

On 06/09/19 20:33, John Larkin wrote:
On Fri, 6 Sep 2019 15:11:33 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.


Mine too.

Cheers

Phil Hobbs

I designed $200M worth of electronics for them, and then they fired me
for insubordination. The idiots didn't understand that engineers are
supposed to be insubordinate.

Of course. Human resources are fungible. (Aren't they?)

Whatever happened to the "personnel department"?
Click to expand...

We don't have one.
 
On Friday, September 6, 2019 at 3:33:09 PM UTC-4, John Larkin wrote:
On Fri, 6 Sep 2019 15:11:33 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 9/6/19 1:03 PM, John Larkin wrote:
On Thu, 5 Sep 2019 18:08:29 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 8:58:19 PM UTC-4, John Larkin wrote:
On Thu, 5 Sep 2019 17:50:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, September 5, 2019 at 5:36:55 PM UTC-4, Winfield Hill wrote:
George Herold wrote...

So this is a bit of an aside, but I need a new gig*.

What's wrong with your present gig? You seem to be
doing well, doing interesting designs and helping to
create new teaching products, what's wrong with that?
Yeah on paper it's my perfect gig.
In practice... I guess we have to be talking person to
person, for the dirty laundry to be discussed.
The bottom line is that almost all my present day
collaboration, happens here (SED) and not at work.
Which sucks*. I need a job where I look forward to
going into work each day, for reasons that are ~1/2 my
fault, that's not true anymore.

George H.


*there's a double suckage, that goes with leaving,
and knowing things will be worse for all the
friends and coworkers left behind.
They are all friends and will understand,
but the double suckage remains.
GH

I didn't have such a dilemma. I got fired.

Hah, I got fired too! we'll we need bar stools to
discuss the details.

Maybe just a delayed fuse on my part.

George h.

Being fired was great. Started my life over.


Mine too.

Cheers

Phil Hobbs

I designed $200M worth of electronics for them, and then they fired me
for insubordination. The idiots didn't understand that engineers are
supposed to be insubordinate.
Click to expand...

As soon as I get a new gig I can talk 'on the air'.

So let me ask you this, we're bringing in phd's for a hire,
my inclination is tell them my situation, after which I'm
totally fine with them taking the job.
(but could scare 'em off... cause no one wants to
maintain my old circuits, including me. :^)

George H.
 
On Wednesday, September 4, 2019 at 1:45:09 PM UTC-4, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.
Click to expand...

Well indeed the oap145 has voltage noise that rises by about 6dB by 100kHz.
Though it appears to flatten off there and not go any higher.

Folder with 'scope Q-FFT's and SRS 730, these pics are a bit cryptic and
I'd have to explain them... well the srs one is fairly obvious.

George H.

https://www.dropbox.com/sh/bl38w9o1gdpqq4x/AADSaSuLdHW8mgpfYOADqbzPa?dl=0
 
On Wednesday, September 11, 2019 at 4:16:51 PM UTC-4, George Herold wrote:
On Wednesday, September 4, 2019 at 1:45:09 PM UTC-4, George Herold wrote:
Hi all, Well the opa124 is EOL, suggested replacement is opa145.
http://www.ti.com/lit/ds/symlink/opa145.pdf
Looks nice. Very low 1/f noise corner. And then I got a little worried
looking a figure 17, which shows voltage noise rising from 10k Hz on.. and then
the graph ends at 100 kHz.

Anyone looked at used this opamp?
I'm going to order a few.

Thx
George H.

Well indeed the oap145 has voltage noise that rises by about 6dB by 100kHz.
Though it appears to flatten off there and not go any higher.

Folder with 'scope Q-FFT's and SRS 730, these pics are a bit cryptic and
I'd have to explain them... well the srs one is fairly obvious.

George H.

https://www.dropbox.com/sh/bl38w9o1gdpqq4x/AADSaSuLdHW8mgpfYOADqbzPa?dl=0
Click to expand...

Dang you can't see those 'scope displays at all.
(John L. how do you take such nice screen shots?)
So for me, the 1MHz Q-fft* The fft is 4 dB per div,
500 kHz span and 250 (246?) kHz center freq.
(The noise looks to peak/ flatten at 150-200kHz.)

100kHz band width is noise into same up stream amp but with
100kHz 2-pole, ~Q=0.707 LP filter.
10 dB/ div. Same freq scale.

The SRS is it's max BW 0-100kHz and ~1000 averages
(the Q-fft are also 1024 averages.)

George H.
(*with a Q-fft you have to divide the power scale in half.
you can do the math, or check it with a known filter
and a noise source.) (my colleague 'did the math' for me..
I can post the relevant section of the manual if anyone wants.)
And there is an interesting question with how small a coherent
signal you can see.. 'buried in the noise' say in some given time.
(to make a Qfft you've got to trigger near the top of your
noise + small signal.. you get more 'small signal' triggers
with a higher trigger level, but less number of traces to average.
Does it go as the time squared, compared to a system that
does the FFT and then averages that?
 
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