I used the output amplifier with gain=4.7. The output of AD711 is as per expectation, i.e. AD711 output = (differential voltage at pin 5 and 4 of AD834) X 4.7

The circuit seems to be so simple, but I do not know where is the mistake…

Can you attach your schematic diagram? I can't seem to find the specific LTX tester you're using, if possible can you give a link or attach documents regarding the LTX tester VI16 module. It'll be a great help in analyzing this issue.…

This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

The idea is to make a desired current run through the RZ variable load. The voltage drop across R5 has to be the same as Vin, so the current is Vin/R5. To achieve that, I inverted it with U8 and added to Vin at U1, so I get a zero voltage at the inverting…