Question

Which of the following is not the advantage of negative feedback?
A. Highly stabilized gain.
B. Reduction in the noise level.
C. Increased bandwidth.
D. Decreased input impedance and increased output impedance.

Answer 1

An electronic amplifier that generally subtracts a fraction of its input to its output, so that the feedback produced opposes the original signal is known as a negative feedback amplifier.

Complete step-by-step solution:

Here in the above diagram, we see a negative feedback amplifier circuit, After the input, the modulation reaches the amplifier circuit and after that, the output has feedback sounds also, So before the sounds reach the ears of the listeners it has a feedback circuit which takes away all the feedback sounds and then again sends it back to the input part to get amplified.
We know that the advantages of negative feedback are as follows,
It has a highly stabilized gain, negative feedback has increased bandwidth, it has decreased output impedance and increased input impedance, it has a reduction in noise level and it will always have less distortion.
So, from the above point, we can say that option D, that is Decreased input impedance and increased output impedance, is the correct option.
Additional Information:
There are many pros and cons in these amplifiers those are as follows:
Pros / advantage:
Negative feedback amplifiers can increase and decrease input impedance, obviously depending upon the type of feedback.
Negative feedback amplifiers can decrease the output impedance again depending upon the type of feedback.
They can increase the bandwidth.
Negative feedback amplifiers can control the step response of an amplifier.
Negative feedback amplifiers can desensitize gain to component variations.
Cons/ Disadvantages:
In negative feedback amplifiers, the gain increases.
Negative feedback amplifiers can lead to instability if they are not designed properly.
Without feedback, the input and output impedances of a negative feedback amplifier can become sensitive to the gain of the amplifier.

Note: These amplifiers if not designed correctly can become unstable, which will result in unwanted behavior such as oscillation. Generally all, electronic devices are non-linear if they provide power gain.