SOLUTION

If the feedback fraction is opposite in value or anti-phase to the input signal, then the feedback is said to be Negative Feedback or degenerative feedback. If the output of the system changes for any reason, then negative feedback affects the input in such a way as to counteract the change.

The feedback amplification factor is given by:

${A_f} = \frac{A}{{1 + A\beta }}\$

where,

A is open-loop gain

Aβ is the loop gain.

Advantages of Negative feedback

1. Negative feedback increases the input impedance of the voltage amplifier.\The output impedance of the voltage amplifier can be further lowered by negative feedback.
2. The transfer gain of the amplifier with feedback can be stabilized against the variations of hybrid parameters of the transistors, or the parameters of the other active devices used in the amplifier.
3. Negative feedback increases the frequency response and the bandwidth of the amplifier. Bandwidth always increases due to negative feedback as the speed of response is directly proportional to the bandwidth.
4. Negative feedback increases the linear range of operation of the amplifier.
5. Negative feedback causes a reduction in noise.
6. Phase distortion is reduced.

Note:-

Negative feedback reduces the actual input signal applied to the basic amplifier which is appropriate for the active device used because the device has to run for a limited time, this reduced distance on the linear region, making its excursion on the load line faster, means the overall speed is now increased. That means more bandwidth!