Keithley 103 nanovolt amplifier architecture question

[David Hess]

The thing which these integrated matched monolithic transistors provide, besides matching and good hfe over a wide current range, is low base spreading resistance which allows for lower noise.  Some discrete transistors also have low base spreading resistance, including transistors with "perforated" and "ring" emitter construction.  The old Zetex "super e-line" transistors would be good, and I am guessing modern high hfe and low Vce saturation parts from other manufacturers.  I think Microchip makes the Zetex parts now.

THAT Corporation has matched quads, but I do not know what kind of construction they use.

Linear Systems has duals, but I do not know if they have low base spreading resistance.

[Overspeed]

The MAT-04 in Figure 6 is configured as the little known Caprio Cross-Coupled Cell, don't see that very often

Long ago we utilized that along with a differential Cherry-Hooper Amp done in SiGe BiCMOS for some MW/MMW very high DR amps and mixers.

Best

Hello

I agree little known Caprio Cross-Coupled Cell , another electronic niche domain ....but I enjoy to learn

Regarding the Amp Op , on the LM394 schematic they use a old LM108 , on your PMUI schematic with MAT04 that a OP-17
I am not an expert in Op Amp but I have seen other schematic ( Mat03 ) with OP-07.

Perhaps SSM2210 can be wired a this schematic , they cost 8 Euro per piece a possible budget and easy to purchase.

Do you think a OP-27 can works as that available , that upgrade OP-07 and that available at acceptable price and quantity but that not a FET.

Regards
OS

[Kleinstein]

The OP27 or a similar modern one is a reasonable choice for the OP-amp with a discrete amplifier. It depends a bit on the frequency range of interest and gain wanted. With high gain one may want a reasonable high GBW op-amp.

[David Hess]

Regarding the Amp Op , on the LM394 schematic they use a old LM108 , on your PMUI schematic with MAT04 that a OP-17
I am not an expert in Op Amp but I have seen other schematic ( Mat03 ) with OP-07.

The LM108 (usually an LM308) was the best part at the time, at least from National.  The uA725, predecessor to the OP-07, would have been suitable but is a Fairchild part.  In general a precision operational amplifier is called for and we have lots of good parts now.

Perhaps SSM2210 can be wired a this schematic , they cost 8 Euro per piece a possible budget and easy to purchase.

The SSM2210 will work fine, but parts like the MAT02E have lower temperature drift which may be called for in more precise applications.

Do you think a OP-27 can works as that available , that upgrade OP-07 and that available at acceptable price and quantity but that not a FET.

The OP-27 and similar parts have all of the advantages of the OP-07 at higher speed and lower noise so will be excellent in a higher bandwidth design.

[Overspeed]

The OP27 or a similar modern one is a reasonable choice for the OP-amp with a discrete amplifier. It depends a bit on the frequency range of interest and gain wanted. With high gain one may want a reasonable high GBW op-amp.

Hello

I search to reach 2000 as gain so 1000 for the fet and x 2 for the Op Amp ... perhaps that better to set a lower gain on the FET stage and increase the final gain by using the OP27

My DC pulsed current is low in the 100 Hz range maximum .

Regards
OS

[Overspeed]

Regarding the Amp Op , on the LM394 schematic they use a old LM108 , on your PMUI schematic with MAT04 that a OP-17
I am not an expert in Op Amp but I have seen other schematic ( Mat03 ) with OP-07.

The LM108 (usually an LM308) was the best part at the time, at least from National.  The uA725, predecessor to the OP-07, would have been suitable but is a Fairchild part.  In general a precision operational amplifier is called for and we have lots of good parts now.

Perhaps SSM2210 can be wired a this schematic , they cost 8 Euro per piece a possible budget and easy to purchase.

The SSM2210 will work fine, but parts like the MAT02E have lower temperature drift which may be called for in more precise applications.

Do you think a OP-27 can works as that available , that upgrade OP-07 and that available at acceptable price and quantity but that not a FET.

The OP-27 and similar parts have all of the advantages of the OP-07 at higher speed and lower noise so will be excellent in a higher bandwidth design.

Hello

I try to locate and secure components with a good life time not to focus on obsolete one as that looks most of the time as saint graal quest .

SSM2210 and OP27 are easy to purchase and the market prices are reasonable and available in SOIC so easy to solder

I start an updated schematic and a BOM and I start the PCB with SOIC foot print

Question : does SSM2210 need a special pcb track / guard ?
Question : rather to use a DC /DC converter for the +15/-15 V can I use a set of 94 x3.7 V)x 2 to genrate +/- with  lithium battery and generate 14.8V with lowest noise ? this circuit electrical consumption shall be very low so a set of battery can do the job

Regards
OS

[Kleinstein]

The SSM2212 does not need special guards. If at all one would consider cut outs to reduce stress. However this would mainly be for long time precision, not for a relative short measurement cycle with current on/off.

For a low voltge amplifier one should not use a +-15 V supply, but less.  So the question is of one can get away with a +-7.2 V or even less. Direct supply from the Li cells could work. It depends a bit on the details how good the PSRR is and how close one gets to the positive rail for the OP27.
SO8 OP-amps use a standard layout - so easy the change if needed.

The discrete amplifier stage will usually not reach a gain of 1000. It would be more like 20 x for JFETs and maybe 100 x for BJTs. With a cascode stage the gain can be a little higher with the JFETs.  So the OP-amps noise and drift may matter and thus look for something better than the TLE2061.
So the OP-amp will naturally provide more of the gain, but this would not be an issue at the relatively low frequency.

[MathWizard]

 In the pic of AN45, I can see the 2 op-amps and 2 JFET's, but are those 2 baby bottles by Figure 4 ?? They don't really look like pens or pencils, 

[mycroft]

These are Jim Willliam's time measurement units :-)

From the first page of AN45:

The circuits in this collection represent our efforts, which
stopped when he (more or less) began sleeping through
the night. Most of the breadboarding occurred between
feedings, with design reviews and discussions during
feedings. As such, the circuits are annotated with the
number of feedings required for their completion; e.g., a
“3-bottle circuit” took three feedings. The circuit’s degree
of difficulty, and Michael’s degree of cooperation, combined
to determine the bottle rating, which is duly recorded in
each figure.

[1audio]

As was mentioned earlier AC is a better solution for measuring low resistance values for several reasons- No thermals, no issues with correcting DC offsets etc. The HP 4328A is an example of how to do it: https://www.hpmemoryproject.org/technics/bench/milliohm/bench_milliohm.htm 
They have got expensive recently, $800, but the principles should be helpful for your project.

[Overspeed]

As was mentioned earlier AC is a better solution for measuring low resistance values for several reasons- No thermals, no issues with correcting DC offsets etc. The HP 4328A is an example of how to do it: https://www.hpmemoryproject.org/technics/bench/milliohm/bench_milliohm.htm 
They have got expensive recently, $800, but the principles should be helpful for your project.

Hello

Thanks

AC measurement genrate skin current that not a problem on most electronic component , that could be a problem for mettalurgy purpose , I use DC reverse current 

Regards
OS

[Kleinstein]

Reversal of current is also a form of AC. A point that could make a difference is a pause between the polarities. This gives time for the inductive effects to settle.

[1audio]

Maybe one of the Vahalla microohmmeters would be better suited?  https://www.ebay.com/sch/i.html?_nkw=vahalla+ohmmeter&_sacat=0&_from=R40&_trksid=p4624852.m570.l1313  I belive they use a reversal technique to remove thermal errors. They also make igniter testers which are specal low current ohmmeters. Vahalla : https://valhallascientific.com/product-category/micro-ohmmeters/

[Overspeed]

Maybe one of the Vahalla microohmmeters would be better suited?  https://www.ebay.com/sch/i.html?_nkw=vahalla+ohmmeter&_sacat=0&_from=R40&_trksid=p4624852.m570.l1313  I belive they use a reversal technique to remove thermal errors. They also make igniter testers which are specal low current ohmmeters. Vahalla : https://valhallascientific.com/product-category/micro-ohmmeters/

Hello

Thanks , Valhalla 4300 is an interesting system , on uOhm they use 10 Amp and 20 mV voltage , a very low value . Schematic will be interesting to watch

Regards
OS

[1audio]

The igniter testers are also interesting. Failure there could be catastrophic. https://valhallascientific.com/shop/igniter-testers/4314-ki-wide-range-ultra-safe-digital-igniter-tester/  One on eBay for $150: https://www.ebay.com/itm/197197314308?chn=ps&norover=1&mkevt=1&mkrid=711-166974-028196-7&mkcid=2&mkscid=101&itemid=197197314308&targetid=2304343365564&device=c&mktype=pla&googleloc=9032039&poi=&campaignid=22556502643&mkgroupid=179708627419&rlsatarget=pla-2304343365564&abcId=10314741&merchantid=8536794&geoid=9032039&gad_source=1&gad_campaignid=22556502643&gbraid=0AAAAAD_QDh9lTNOWETSqcDx6v_PH-8M56&gclid=Cj0KCQjw6bfHBhDNARIsAIGsqLhJg4POnkLEaSvVkMmGPx2EUrYWICVpyZm3zdbCUcu4HOu0jXaZXaoaAsOREALw_wcB