Departures from Ideal Op-amp

Though common and inexpensive op-amps like the 741 come remarkably close to the ideal op-amp, there are practical limitations which come into play in circuit design. Some of the things which cause problems are

The input current isn't exactly zero. The input offset current isn't exactly zero either. The input impedance isn't infinite. There is a limited common mode voltage range. The output impedance isn't zero. There are voltage gain limitations including phase shifts. There is a finite input offset voltage. There is a finite slew rate. There is some temperature dependence.