High side current sensing with variable gain

[phaedrus]

Thanks Eric.Much obliged for your pointers.

hi,
Rechecked the LF411 you were correct.
This LTS sim is close to what you are looking for.

 

[ericgibbs]

Thanks Eric.Much obliged for your pointers.

hi,
An important point you should be aware of is the response of the circuit when you substitute a transistor for the JFET as shown in the original circuit.

If you are required to monitor the 200mA/20mA over a close tolerance the transistor response is OK, but if you need to monitor the current 200mA/20mA from say 0mA to maximum mA the the JFET is the correct solution.