Circuit design of branded electrometers

[Neomys Sapiens]

The silence came because forum participants know nothing but Keithley instruments and a single source of information - low level measurements handbook.
And personally I am engaged in reading Soviet books and designing my future electrometric buffer for a DMM based on the AD549
I suggest that we continue to frighten local residents with Soviet devices. They already know our bears, but electrometers are unlikely
I would very much like to discuss why manufacturers use printed circuit boards to conduct input circuits. What own current can be generated by the Board material and what is the influence of environmental factors. But I know it's impossible, because those who know won't say anything

Sure, blame the bears for everything. 

[Kirill V.]

Ha-ha! But still let's discuss my primitive circuit
I completely forgot to clarify that the op amp has a bootstrapped supply related to the out node.
And also I want to apply the microcurrent mode of operation of transistors say 50 mkA collector current. This is very attractive because transistors will emit very little heat. Interesting criticism

[Neomys Sapiens]

Ha-ha! But still let's discuss my primitive circuit
I completely forgot to clarify that the op amp has a bootstrapped supply related to the out node.
And also I want to apply the microcurrent mode of operation of transistors say 50 mkA collector current. This is very attractive because transistors will emit very little heat. Interesting criticism

I just started to read through your thread when I found your comment to strannik2039, which I could not resist to answer. But I'm not yet very knowledgeable in electrometers. Somewhere I have a circuit diagram from a High-Impedance voltmeter from Siemens, but I think it is rather the normal 'Transistorvoltmeter' stuff. As I have analysed and cross-indexed most of the semiconductor appnotes I could ever reach, I can surely make a topical search and excerpt, in case I find something.

[Kleinstein]

With a weak bootstrapped supply there could be a problem with the load to the OP, when the transistor stage goes into current limiting. It depends on the details, but usually a bootstrapped OP should only drive a small load.

The circuit gets more readable with dots to mark connections if needed.

The input to the current mirror could start from a lower voltage - but that is a minor detail.

[Kirill V.]

Somewhere I have a circuit diagram from a High-Impedance voltmeter from Siemens, but I think it is rather the normal 'Transistorvoltmeter' stuff. As I have analysed and cross-indexed most of the semiconductor appnotes I could ever reach, I can surely make a topical search and excerpt, in case I find something.

I'd like to take a look at this

With a weak bootstrapped supply there could be a problem with the load to the OP, when the transistor stage goes into current limiting. It depends on the details, but usually a bootstrapped OP should only drive a small load.

The circuit gets more readable with dots to mark connections if needed.

The input to the current mirror could start from a lower voltage - but that is a minor detail.

OK, thanks! Apparently you are referring to bootstrapped supply from zeners that are biased by current generators - as is often done, right? But I'm leaning towards independent sources like in K617. I do not think that in this case there will be problems with the current limiting circuit.
But what I'm concerned about is that the output stage of the op amp will be taking an increased current which will cause additional heat to be released inside the amp. In principle, this problem can be solved at least by adding a buffer amplifier. But there should be more elegant solutions, in my opinion.
I also don't like the fact that the output of the op amp has a constant offset of at least 600 mV, which increases when the load current is limited. This offset is translated to the input reduced by Aol times. It's not critical I'm just a bit of a perfectionist
This is a Splan and I don't know how to make it draw dots in nodes, sorry I highlight branches with color

[coppercone2]

Sure, blame the bears for everything. 

What is this device in the snow?

I just get women in bikinis googling iskra site

[Kirill V.]

Sure, blame the bears for everything. 

What is this device in the snow?

I just get women in bikinis googling iskra site

It seems to be a unique high-voltage laboratory in Leningrad (now Saint Petersburg). It was used in the design of high-voltage power lines. These are transformers that can produce more than a million volts.
It's funny, but I've learned to dot the nodes

[Neomys Sapiens]

Sure, blame the bears for everything. 

What is this device in the snow?

I just get women in bikinis googling iskra site

Not exactly. And sorry - it should have been 'Istra', not 'Iskra'.
Look here:
https://www.atlasobscura.com/places/abandoned-marx-generator