On Friday, March 13, 2015 at 8:30:27 PM UTC-4, George Herold wrote:> On Friday, March 13, 2015 at 8:08:22 PM UTC-4, Tim Wescott wrote: > > On Fri, 13 Mar 2015 13:11:16 -0700, George Herold wrote: > > > > > On Friday, March 13, 2015 at 2:44:51 PM UTC-4, Tim Wescott wrote: > > >> On Fri, 13 Mar 2015 10:49:11 -0700, George Herold wrote: > > >> > > >> > On Friday, March 13, 2015 at 1:23:46 PM UTC-4, Jan Panteltje wrote: > > >> >> On a sunny day (Fri, 13 Mar 2015 10:10:38 -0700 (PDT)) it happened > > >> >> George Herold <gherold@teachspin.com> wrote in > > >> >> <ad164713-93a0-48f2-919e-b5f94b53a806@googlegroups.com>: > > >> >> > > >> >> >Hi guys (and dolls), So if you read in JL's TI opamp thread, > > >> >> >I am having noise issues in our laser diode. > > >> >> >I turns out (I think) that the extra noise is coming from my Piezo > > >> >> >drive. > > >> >> >The original circuit used a PA141 from Apex. > > >> >> >(I can't find a schematic on-line, but I have a hard copy.) > > >> >> >Several years ago this HV opamp went away and the recommended > > >> >> >replacement from Apex was the PA314 > > >> >> >https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf > > >> >> > > > >> >> >I basically plugged it in, it worked, and I forgot about it. > > >> >> >Well it's not quite the same... a few differences but the big one > > >> >> >is the noise... Some gawd awful 350 uV rms in a 10 k Hz BW... > > >> >> >(~350nV/rt Hz.) And no spec on the low freq. 1/f noise. > > >> >> > > > >> >> >So I've been trying to beat the noise down in the current circuit, > > >> >> >but with no luck. I use it as a x10 inverting amp. Rin= 10 k ohm > > >> >> >and Rf= > > >> >> >100k ohm. I tried rolling off the gain with 100pf in parallel with > > >> >> >Rf, but this lead to low level oscillations.. (scratch scratch.) I > > >> >> >then tried adding more compensation capacitance from 10 pF to ~70 > > >> >> >pF but this did nothing. > > >> >> > > > >> >> >Any ideas for trying to salvage this circuit? > > >> >> >I could live with a bandwidth of 5 kHz or so. > > >> >> > > > >> >> >TIA George H. > > >> >> > > >> >> > > >> >> Sometimes {tm) > > >> >> ------||---10k ---- > > >> >> | 1n | > > >> >> |----------||------ | > > >> >> | 100p | > > >> >> 10k ----- 100 k----------------- > > >> >> | | > > >> >> --- - | > > >> >> > ----- > > >> >> --- + > > >> >> > > >> >> > > >> > OK, I'll give it a try... I was thinking some resistance in series > > >> > with the 100pF..(?) > > >> > > > >> > (I just ordered some LTC6090's from DK...) > > >> > > > >> > I also noticed that the PA341 has been replaced with the PA441.. 30 > > >> > times less noise! > > >> > > > >> > > > >> Maybe they were getting lots of complaints! Is it pin-compatible? > > > > > > Yup.. I order one of those too.. but only 1.. ~$50 each! > > > > Apex parts definitely make you pay for the privilege of not having to roll > > your own amp. It's worth it if your volume is low and the cost of failure > > is high. > Yeah, we've been happily paying that cost for years. > Now due to their crappy opamp, > combined with my lack of due diligence...I'm not a complete idiot.. the laser's are all tested with the SAS linewidth, ~10 MHz ideal, and power broadened to ~20Mhz at a guess. And this 2-4 MHz "junk" was small enough to get through my net, and still screw up something else. (sorry, I'll be kicking myself all weekend.) George H.> the return shipping costs to India > will make it seem like nothing. > (at least I found it now, I think we've only shipped one to India... > and you never know we might find someone there > who can handle a soldering iron.) > > George H. > > > > -- > > > > Tim Wescott > > Wescott Design Services > > http://www.wescottdesign.com
Apex HV opamp issues.
Started by ●March 13, 2015
Reply by ●March 13, 20152015-03-13
Reply by ●March 13, 20152015-03-13
On Fri, 13 Mar 2015 17:30:23 -0700, George Herold wrote:> On Friday, March 13, 2015 at 8:08:22 PM UTC-4, Tim Wescott wrote: >> On Fri, 13 Mar 2015 13:11:16 -0700, George Herold wrote: >> >> > On Friday, March 13, 2015 at 2:44:51 PM UTC-4, Tim Wescott wrote: >> >> On Fri, 13 Mar 2015 10:49:11 -0700, George Herold wrote: >> >> >> >> > On Friday, March 13, 2015 at 1:23:46 PM UTC-4, Jan Panteltje >> >> > wrote: >> >> >> On a sunny day (Fri, 13 Mar 2015 10:10:38 -0700 (PDT)) it >> >> >> happened George Herold <gherold@teachspin.com> wrote in >> >> >> <ad164713-93a0-48f2-919e-b5f94b53a806@googlegroups.com>: >> >> >> >> >> >> >Hi guys (and dolls), So if you read in JL's TI opamp thread, >> >> >> >I am having noise issues in our laser diode. >> >> >> >I turns out (I think) that the extra noise is coming from my >> >> >> >Piezo drive. >> >> >> >The original circuit used a PA141 from Apex. >> >> >> >(I can't find a schematic on-line, but I have a hard copy.) >> >> >> >Several years ago this HV opamp went away and the recommended >> >> >> >replacement from Apex was the PA314 >> >> >> >https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf >> >> >> > >> >> >> >I basically plugged it in, it worked, and I forgot about it. >> >> >> >Well it's not quite the same... a few differences but the big >> >> >> >one is the noise... Some gawd awful 350 uV rms in a 10 k Hz >> >> >> >BW... (~350nV/rt Hz.) And no spec on the low freq. 1/f noise. >> >> >> > >> >> >> >So I've been trying to beat the noise down in the current >> >> >> >circuit, but with no luck. I use it as a x10 inverting amp. >> >> >> >Rin= 10 k ohm and Rf= >> >> >> >100k ohm. I tried rolling off the gain with 100pf in parallel >> >> >> >with Rf, but this lead to low level oscillations.. (scratch >> >> >> >scratch.) I then tried adding more compensation capacitance from >> >> >> >10 pF to ~70 pF but this did nothing. >> >> >> > >> >> >> >Any ideas for trying to salvage this circuit? >> >> >> >I could live with a bandwidth of 5 kHz or so. >> >> >> > >> >> >> >TIA George H. >> >> >> >> >> >> >> >> >> Sometimes {tm) >> >> >> ------||---10k ---- >> >> >> | 1n | >> >> >> |----------||------ | >> >> >> | 100p | >> >> >> 10k ----- 100 k----------------- >> >> >> | | >> >> >> --- - | >> >> >> > ----- >> >> >> --- + >> >> >> >> >> >> >> >> > OK, I'll give it a try... I was thinking some resistance in series >> >> > with the 100pF..(?) >> >> > >> >> > (I just ordered some LTC6090's from DK...) >> >> > >> >> > I also noticed that the PA341 has been replaced with the PA441.. >> >> > 30 times less noise! >> >> > >> >> > >> >> Maybe they were getting lots of complaints! Is it pin-compatible? >> > >> > Yup.. I order one of those too.. but only 1.. ~$50 each! >> >> Apex parts definitely make you pay for the privilege of not having to >> roll your own amp. It's worth it if your volume is low and the cost of >> failure is high.> Yeah, we've been happily paying that cost for years. > Now due to their crappy opamp, > combined with my lack of due diligence... > the return shipping costs to India will make it seem like nothing. > (at least I found it now, I think we've only shipped one to India... > and you never know we might find someone there who can handle a > soldering iron.)See if you can get Pimpom's email addy -- he's out in the sticks somewhere, but maybe you could ship it to him for the repair. (or have them toss it in the dumpster and just send a new one?) -- www.wescottdesign.com
Reply by ●March 14, 20152015-03-14
On a sunny day (Fri, 13 Mar 2015 13:45:11 -0700) it happened John Larkin <jlarkin@highlandtechnology.com> wrote in <jji6gadtd50u67np8f9e1d15f3rdv7nt3g@4ax.com>:> >You could try my cheap and almost-famous optocoupler-based HV >amplifier. > >https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPGThats is a keeper.
Reply by ●March 14, 20152015-03-14
On Sat, 14 Mar 2015 09:11:16 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Fri, 13 Mar 2015 13:45:11 -0700) it happened John Larkin ><jlarkin@highlandtechnology.com> wrote in ><jji6gadtd50u67np8f9e1d15f3rdv7nt3g@4ax.com>: >> >>You could try my cheap and almost-famous optocoupler-based HV >>amplifier. >> >>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG > >Thats is a keeper.It likes capacitive loads, which become the dominant pole in the feedback loop. With that sort of compensation, more C load just makes it more stable. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 14, 20152015-03-14
On Sat, 14 Mar 2015 09:11:16 +0000, Jan Panteltje wrote:> On a sunny day (Fri, 13 Mar 2015 13:45:11 -0700) it happened John Larkin > <jlarkin@highlandtechnology.com> wrote in > <jji6gadtd50u67np8f9e1d15f3rdv7nt3g@4ax.com>: >> >>You could try my cheap and almost-famous optocoupler-based HV amplifier. >> >>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG > > Thats is a keeper.Ooooh, I wish I were still working at FLIR. Our head analog engineer was excellent, but very averse to odd topologies and to circuits that he didn't think would simulate well. Tossing this schematic in front of him in a meeting would be like tossing a cat into a cage full of antisocial dogs. -- www.wescottdesign.com
Reply by ●March 14, 20152015-03-14
On Sat, 14 Mar 2015 13:43:41 -0500, Tim Wescott <tim@seemywebsite.com> wrote:>On Sat, 14 Mar 2015 09:11:16 +0000, Jan Panteltje wrote: > >> On a sunny day (Fri, 13 Mar 2015 13:45:11 -0700) it happened John Larkin >> <jlarkin@highlandtechnology.com> wrote in >> <jji6gadtd50u67np8f9e1d15f3rdv7nt3g@4ax.com>: >>> >>>You could try my cheap and almost-famous optocoupler-based HV amplifier. >>> >>>https://dl.dropboxusercontent.com/u/53724080/Optos/HVamp.JPG >> >> Thats is a keeper. > >Ooooh, I wish I were still working at FLIR. Our head analog engineer was >excellent, but very averse to odd topologies and to circuits that he >didn't think would simulate well. Tossing this schematic in front of him >in a meeting would be like tossing a cat into a cage full of antisocial >dogs.If he was adverse to odd designs, how did the E45 software wind up so weird? It's not a regular camera interface, it's a network device over USB with a bizarre cable. If you use it one one USB port, and change ports next time, even a different slot on a hub, the PC software forgets that it exists. The thermal part works pretty well. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 14, 20152015-03-14
George Herold wrote...> > Hi guys (and dolls), So if you read in JL's TI opamp thread, > I am having noise issues in our laser diode. > I turns out (I think) that the extra noise is coming > from my Piezo drive. > The original circuit used a PA141 from Apex. > (I can't find a schematic on-line, but I have a hard copy.) > Several years ago this HV opamp went away and the > recommended replacement from Apex was the PA314 > https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf > > I basically plugged it in, it worked, and I forgot about it. > Well it's not quite the same... a few differences but the big one > is the noise... Some gawd awful 350 uV rms in a 10 k Hz BW... > (~350nV/rt Hz.) And no spec on the low freq. 1/f noise. > > So I've been trying to beat the noise down in the current circuit, > but with no luck. I use it as a x10 inverting amp. Rin= 10 k ohm and > Rf= 100k ohm. I tried rolling off the gain with 100pf in parallel > with Rf, but this lead to low level oscillations.. (scratch scratch.) > I then tried adding more compensation capacitance from 10 pF to ~70 pF > but this did nothing. > > Any ideas for trying to salvage this circuit? > I could live with a bandwidth of 5 kHz or so. > > TIA > George H.Yep, most of the APEX opamps made with MOSFET input transistors are very noisy, especially at low frequencies. For example, the PA141 spec says 50uV rms, over a 10kHz bandwidth. By comparison the PA341 spec is 337uV rms. Whoa!! Their JFET-input opamps are much better, for example the PA97 specs 2uV rmw over 10kHz. So you could change to one of those types. Or you could make your own HV amplifier, using a low-voltage JEFT opamp to control MOSFET power transistors. We show an example in Figure 3.75 in AoE 2nd edition (also see Figure 6.47). These amplifiers can be even more quiet. I updated the circuit for AoE-III, see Figure 3.111. [Note, AoE-III is being printed and will be shipping in a week or two.] A more advanced circuit is set for the AoE x-Chapter book (for the time being it's Figure 4x.50 in section 4x.18), where there's a lengthy careful analysis of the design, and its performance into large capacitive loads, etc. A refined version of that circuit is in development for a freebie PCB, so y'all can easily make your own. It's my Rowland EE Labs AMP-62A project, and here's a schematic: https://www.dropbox.com/s/cqpoyr2toj1c7pt/AMP-62A-2_sch_r3_fast.pdf?dl=0 https://www.dropbox.com/s/0e5x0mhr5ldwjho/AMP-62A-2_pcb_r3_3D-image.JPG?dl=0 -- Thanks, - Win
Reply by ●March 14, 20152015-03-14
On 14 Mar 2015 13:32:45 -0700, Winfield Hill <hill@rowland.harvard.edu> wrote:>George Herold wrote... >> >> Hi guys (and dolls), So if you read in JL's TI opamp thread, >> I am having noise issues in our laser diode. >> I turns out (I think) that the extra noise is coming >> from my Piezo drive. >> The original circuit used a PA141 from Apex. >> (I can't find a schematic on-line, but I have a hard copy.) >> Several years ago this HV opamp went away and the >> recommended replacement from Apex was the PA314 >> https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf >> >> I basically plugged it in, it worked, and I forgot about it. >> Well it's not quite the same... a few differences but the big one >> is the noise... Some gawd awful 350 uV rms in a 10 k Hz BW... >> (~350nV/rt Hz.) And no spec on the low freq. 1/f noise. >> >> So I've been trying to beat the noise down in the current circuit, >> but with no luck. I use it as a x10 inverting amp. Rin= 10 k ohm and >> Rf= 100k ohm. I tried rolling off the gain with 100pf in parallel >> with Rf, but this lead to low level oscillations.. (scratch scratch.) >> I then tried adding more compensation capacitance from 10 pF to ~70 pF >> but this did nothing. >> >> Any ideas for trying to salvage this circuit? >> I could live with a bandwidth of 5 kHz or so. >> >> TIA >> George H. > > Yep, most of the APEX opamps made with MOSFET input transistors > are very noisy, especially at low frequencies. For example, the > PA141 spec says 50uV rms, over a 10kHz bandwidth. By comparison > the PA341 spec is 337uV rms. Whoa!! Their JFET-input opamps > are much better, for example the PA97 specs 2uV rmw over 10kHz. > So you could change to one of those types. > > Or you could make your own HV amplifier, using a low-voltage > JEFT opamp to control MOSFET power transistors. We show an > example in Figure 3.75 in AoE 2nd edition (also see Figure > 6.47). These amplifiers can be even more quiet. I updated > the circuit for AoE-III, see Figure 3.111. [Note, AoE-III > is being printed and will be shipping in a week or two.] > > A more advanced circuit is set for the AoE x-Chapter book > (for the time being it's Figure 4x.50 in section 4x.18), > where there's a lengthy careful analysis of the design, > and its performance into large capacitive loads, etc. > > A refined version of that circuit is in development for a > freebie PCB, so y'all can easily make your own. It's my > Rowland EE Labs AMP-62A project, and here's a schematic: > https://www.dropbox.com/s/cqpoyr2toj1c7pt/AMP-62A-2_sch_r3_fast.pdf?dl=0 > https://www.dropbox.com/s/0e5x0mhr5ldwjho/AMP-62A-2_pcb_r3_3D-image.JPG?dl=0 > >The MP118 is JFET input, and noise is modeled in my Spice subcircuit. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●March 14, 20152015-03-14
On 14 Mar 2015 13:32:45 -0700, Winfield Hill <hill@rowland.harvard.edu> wrote:>George Herold wrote... >> >> Hi guys (and dolls), So if you read in JL's TI opamp thread, >> I am having noise issues in our laser diode. >> I turns out (I think) that the extra noise is coming >> from my Piezo drive. >> The original circuit used a PA141 from Apex. >> (I can't find a schematic on-line, but I have a hard copy.) >> Several years ago this HV opamp went away and the >> recommended replacement from Apex was the PA314 >> https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf >> >> I basically plugged it in, it worked, and I forgot about it. >> Well it's not quite the same... a few differences but the big one >> is the noise... Some gawd awful 350 uV rms in a 10 k Hz BW... >> (~350nV/rt Hz.) And no spec on the low freq. 1/f noise. >> >> So I've been trying to beat the noise down in the current circuit, >> but with no luck. I use it as a x10 inverting amp. Rin= 10 k ohm and >> Rf= 100k ohm. I tried rolling off the gain with 100pf in parallel >> with Rf, but this lead to low level oscillations.. (scratch scratch.) >> I then tried adding more compensation capacitance from 10 pF to ~70 pF >> but this did nothing. >> >> Any ideas for trying to salvage this circuit? >> I could live with a bandwidth of 5 kHz or so. >> >> TIA >> George H. > > Yep, most of the APEX opamps made with MOSFET input transistors > are very noisy, especially at low frequencies. For example, the > PA141 spec says 50uV rms, over a 10kHz bandwidth. By comparison > the PA341 spec is 337uV rms. Whoa!! Their JFET-input opamps > are much better, for example the PA97 specs 2uV rmw over 10kHz. > So you could change to one of those types. > > Or you could make your own HV amplifier, using a low-voltage > JEFT opamp to control MOSFET power transistors. We show an > example in Figure 3.75 in AoE 2nd edition (also see Figure > 6.47). These amplifiers can be even more quiet. I updated > the circuit for AoE-III, see Figure 3.111. [Note, AoE-III > is being printed and will be shipping in a week or two.] > > A more advanced circuit is set for the AoE x-Chapter book > (for the time being it's Figure 4x.50 in section 4x.18), > where there's a lengthy careful analysis of the design, > and its performance into large capacitive loads, etc. > > A refined version of that circuit is in development for a > freebie PCB, so y'all can easily make your own. It's my > Rowland EE Labs AMP-62A project, and here's a schematic: > https://www.dropbox.com/s/cqpoyr2toj1c7pt/AMP-62A-2_sch_r3_fast.pdf?dl=0 > https://www.dropbox.com/s/0e5x0mhr5ldwjho/AMP-62A-2_pcb_r3_3D-image.JPG?dl=0 > >I don't understand the Q8-Q10 string. Is that safe? -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 14, 20152015-03-14
John Larkin wrote...> >On 14 Mar 2015 13:32:45 -0700, Winfield Hill ><hill@rowland.harvard.edu> wrote: > >>George Herold wrote... >>> >>> Hi guys (and dolls), So if you read in JL's TI opamp thread, >>> I am having noise issues in our laser diode. >>> I turns out (I think) that the extra noise is coming >>> from my Piezo drive. >>> The original circuit used a PA141 from Apex. >>> (I can't find a schematic on-line, but I have a hard copy.) >>> Several years ago this HV opamp went away and the >>> recommended replacement from Apex was the PA314 >>> https://apexanalog-public.sharepoint.com/Resources/PA341U.pdf >>> >>> I basically plugged it in, it worked, and I forgot about it. >>> Well it's not quite the same... a few differences but the big one >>> is the noise... Some gawd awful 350 uV rms in a 10 k Hz BW... >>> (~350nV/rt Hz.) And no spec on the low freq. 1/f noise. >>> >>> So I've been trying to beat the noise down in the current circuit, >>> but with no luck. I use it as a x10 inverting amp. Rin= 10 k ohm and >>> Rf= 100k ohm. I tried rolling off the gain with 100pf in parallel >>> with Rf, but this lead to low level oscillations.. (scratch scratch.) >>> I then tried adding more compensation capacitance from 10 pF to ~70 pF >>> but this did nothing. >>> >>> Any ideas for trying to salvage this circuit? >>> I could live with a bandwidth of 5 kHz or so. >>> >>> TIA >>> George H. >> >> Yep, most of the APEX opamps made with MOSFET input transistors >> are very noisy, especially at low frequencies. For example, the >> PA141 spec says 50uV rms, over a 10kHz bandwidth. By comparison >> the PA341 spec is 337uV rms. Whoa!! Their JFET-input opamps >> are much better, for example the PA97 specs 2uV rmw over 10kHz. >> So you could change to one of those types. >> >> Or you could make your own HV amplifier, using a low-voltage >> JEFT opamp to control MOSFET power transistors. We show an >> example in Figure 3.75 in AoE 2nd edition (also see Figure >> 6.47). These amplifiers can be even more quiet. I updated >> the circuit for AoE-III, see Figure 3.111. [Note, AoE-III >> is being printed and will be shipping in a week or two.] >> >> A more advanced circuit is set for the AoE x-Chapter book >> (for the time being it's Figure 4x.50 in section 4x.18), >> where there's a lengthy careful analysis of the design, >> and its performance into large capacitive loads, etc. >> >> A refined version of that circuit is in development for a >> freebie PCB, so y'all can easily make your own. It's my >> Rowland EE Labs AMP-62A project, and here's a schematic: >> https://www.dropbox.com/s/cqpoyr2toj1c7pt/AMP-62A-2_sch_r3_fast.pdf?dl=0 >> https://www.dropbox.com/s/0e5x0mhr5ldwjho/AMP-62A-2_pcb_r3_3D-image.JPG?dl=0> > I don't understand the Q8-Q10 string. Is that safe?Absolutely. Avalanche is your friend, provided you keep the power dissipation under control. If we assume about 600V avalanche, at 0.5mA that's a very relaxed 300mW. The lowest-current series current-source avalanches first, then the next highest, and so on. So the current-source varies by about maybe up to 0.1mA over voltage. But hey, that's far better than using 2W carbon pullup resistors! Another scheme I like is the MOSFETs wired in cascode, but this requires six series resistors to handle 1kV. But it does let you double or triple the pullup current. -- Thanks, - Win
