An opamp circuit was given in the homework forum: There the circuit was analyzed with the usual assumptions of opamp ideality. But, if the circuit is analyzed with one change to ideality, namely the opamp voltage gain is set to 7 rather than ∞ (this brings with it the change that v+ ≠ v- any more), the calculated overall circuit gain, Vout/Vin, is greater than 7. How can this be? I think I know the answer, but I pose this for the readers to think about and discuss. Edit: I forgot to mention this: Exchange the + and - opamp inputs (or set the opamp gain to -7).