The common mistakes done by students in CAT 3:

Signal generator is used in square wave generation circuit 
Signal generator is used in RC phase shift oscillator
Clippers are explained without op-amp (But oscillator circuit written using op-amp).

Take care of such things in the main Exam. Wish you best of luck for u r main exam.

Final Internal Marks

I wish you Best of Luck for your CAT 3 as well as for main exams. For any discussion you are most welcome. Now give highest priority to your studies.