I'm designing a RIAA pre-amplifier based on the 2 op-amps from an NE5532 package. It seems that something is wrong, because the output of the 2nd stage is giving a 400V output which is way above the power rail voltage. Is it correct?
The 1st voltmeter, XM1, is measuring the input voltage; the 2nd voltmeter, XM2, is measuring the output voltage of the 1st stage; and the 3rd voltmeter, XM3, is measuring the output voltage of the second op-amp, across 100k R7.
Best Answer
If it is SPICE's AC analysis it's not surprising.
In AC analysis, SPICE figures out the small-signal linearized model of the system, then applies the input voltage to that model, assuming it is linear. There is no "resonableness" checking, or any attention paid to nonlinear effects of any sort -- and an op-amp hitting the rails is certainly a nonlinear effect.
It is your responsibility, when using AC analysis, to verify that your system behavior is consistent with a linearized model. If it is not, then you need to use transient (i.e., full-blown nonlinear) analysis.
Try a transient analysis with the same input -- you should see massive clipping on that second stage output.