Please give explanation considering opamp as ideal one as well as practical one.
I got the explanation here. Decompensated Operational Amplifiers
Ideal op amp: stable with infinite bandwidth.
Practical: look for opamps that are guaranteed "unity gain stable" (most modern op amps are unity gain stable). The bandwidth can be determined by looking at the "unity gain bandwidth" or sometimes the "gain-bandwidth product." The bandwidth can be further limited for large amplitude signals by the slew rate, usually expressed as the change in output voltage per unit time.