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TINA/Spice/OPA548: Problem with the OPA548 simulation

Part Number: OPA548

Tool/software: TINA-TI or Spice Models

Hello,

i am trying to do a calibration and for this reason i have to use the sinus signal of a function generator. My generator can provide a signal up to 200 mA @10V p, but of course i will try to use less current if possible.  My "electrical load: 0,35 Ohm" needs current up to  +-1,2 A which corresponds to +-0,5V (that's the voltage limit) at 50 Hz. So i the first idea was to use the LM 1875 which is connected with an electrical transformer 1/20 and then using the generator i would be able to set the voltage where i want to . This idea is ok and it works  fine, at least at a simulation level. The next idea is to use the OPA548 having a gain 1.  For this reason i have done a simulation using TINA which  does not give me the results i would like to see and in order to be more exact the output seems to be a bit higher than the input. In this case the IC that gets this signal would be destroyed(only voltages up to +-0,5V are allowed. Could someone tell me if there is something wrong regarding my simulation. 
Here is my circuit and the inputs/outputs as well.

 

As you see the VM2 output is slightly bigger, than the VG1 which is not supposed to happen.
And something more-->In the Datasheet ,Figure 26 can be found the application example i simulated and it is practically what i need. There is also a Resistor (Riso). Why is this resistor used for?

Regards,
George