I have a hard time to understand why two different opamps in a substractor configuration deliver highly different output in a TINA simulation. At the end I try to implement a high impedance differential aplifier (instrumentation amplifier), which second stage is a subtractor, and I got very different result with different opamps in simulation.
So I first read some basics here: http://www.ti.com/lit/an/slyt213/slyt213.pdf. They explain an instrumentation aplifier as well as simple substractor and in regard to the later there is a formula for Vout which contains only the values for input voltages and external resistors.
So I think then, the particular opamp model does not matter at all for this configuration and DC operation.
Now in TINA I made a DC operation point simulation, for an ideal opamp, for TL082 and for LM7321. The schematic shows my configuration.
Now with an ideal opamp I get the correct 50mV at the output, with LM7321 and 9V supply I get something around 45mV which I suppose is stil OK, but with TL082 there is 1.52V at the output (but the circuitlab simulation results in exactly 50mV). What do I miss? Is it a buggy spice macro in TINA or is there something else in TINA or in the datasheets I should consider or am missing?
I would like to use TL082 because its cheap and I have already some in stock bought as "general purpose opamp".
Please educate me a little :-)