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.
opa145
Started by ●September 4, 2019
Reply by ●September 4, 20192019-09-04
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.) 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
Reply by ●September 4, 20192019-09-04
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. 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
Reply by ●September 4, 20192019-09-04
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) -- 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
Reply by ●September 4, 20192019-09-04
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. 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
Reply by ●September 5, 20192019-09-05
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? -- Thanks, - Win
Reply by ●September 5, 20192019-09-05
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. ;) 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
Reply by ●September 5, 20192019-09-05
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> > > -- > Thanks, > - Win
Reply by ●September 5, 20192019-09-05
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. >GHI didn't have such a dilemma. I got fired.
Reply by ●September 5, 20192019-09-05
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. ;) >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
