Positive feedback:
If the feedback single (i.e. voltage or current) is applied in such a way that is in phase with the input and thus increase it, then it is called as positive feedback.
Sometimes, it is also known as regenerative feedback. The concept of positive feedback Here, both amplifier and feedback network; introduce a phase shift of 1800 the result is a 3600 phase around the loop and thus causing the feedback voltage Vf to be a phase with the input signal Vi Since positive feedback causes excessive distortion. However, because of its capability of increasing the power of the original signal, it is used in oscillator.X0/(Xi (1-Aβ))
Af = A/(1-Aβ)
This is the gain of the amplifier with positive feedback which is increased due to positive feedback. Because is the only advantages of positive feedback because this is one condition for the amplifier to be work as an oscillator.
Disadvantages
- The stability of circuit will be reduced or decrease with increase in gain.
- The bandwidth also decreases with increase in gain.
- The distortion will also increase.
- The noise will also increase.