Feedback and it's Classification

Feedback: Feedback is the process of taking a part or portion of the output signal and feeding it back to the input circuit. The fed back signal can be in phase or out of phase with the original input signal.

Types of Feedback: 

1. Positive feedback (Regenerative)
2. Negative feedback (Degenerative) 

1. Positive feedback (Regenerative): If the original input signal and the feedback signal are in phase, the feedback is called as positive feedback. Positive feedback is used in oscillators to generate desired wave forms. 
2. Negative feedback (Degenerative): If these two signals are out of phase then the feedback is called as negative feedback. Negative feedback is very important for most of the amplifiers.

Negative feedback is also called feedback topology and its classification is shown in here