What are different characteristics of an ideal operational amplifier? 

Ans: Characteristics of an ideal Operational Amplifier:

(1) Infinite voltage gain A

(2) Infinite input resistance R_I so that almost any signal source can drive it and there is no loading of preceding stage.

(3) Zero  output  resistance  Ro,  so  that  output  can  drive  an  infinite  number  of  other devices.

(4) Zero output voltage when input voltage is zero.

(5) Infinite bandwidth so that any frequency signals from 0 to ∝ HZ can be amplified without attenuation.

(6) Infinite common-mode rejection  ratio,  so  that output  common-mode  noise voltage is zero.

(7) Infinite slew rate so that output voltage changes take place simultaneously with input voltage changes.