Ideal operational amplifier কী?

The ideal model assumes: (i) no current enters either input, $i_+ = i_- = 0$ (infinite input impedance); (ii) the output imposes its voltage whatever the current drawn (zero output impedance); (iii) infinite gain, $\mu \to \infty$. In the linear regime ($\abs{V_s} < V_{\mathrm{sat}}$) the third assumption forces

the two inputs sit at the same potential (a “virtual short circuit”) although no current flows between them.