Advantages of Negative Feedback Amplifier:
There are numerous advantages of negative feedback amplifier which outweigh its only drawback of reduction in gain. Among the advantages are :
1. Gain Stability: The voltage gain of an amplifier with negative feedback is given as Af = A/(1 + Aβ). If Aβ >> 1 then the expression becomes Af = 1/β i.e., overall gain of feedback amplifier Af is independent of internal gain and depends only on feedback ratio β, and β in turn depends on the passive elements such as resistors. Resistors remain fairly constant and so the gain is stabilized.
2. Reduced Nonlinear Distortion: A large signal stage has nonlinear distortion which is reduced by a factor (1 + Aβ) when negative feedback is used.
3. Reduced Noise: There is always a noise voltage in the amplifier which is reduced by a factor (1 + Aβ) when negative feedback is used.
4. Increased Bandwidth (or Improved Frequency Response): The bandwidth (BW) of an amplifier without feedback is equal to the separation between 3-dB frequencies f1 and f2. If A is the gain then gain-bandwidth product is A x BW. With the negative feedback the amplifier gain is reduced and since gain bandwidth product has to remain constant in both cases, obviously the bandwidth will increase to compensate for the reduction in gain.
5. Increased Input Impedance: The input impedance of the amplifier with negative feedback is increased by a factor (1 + Aβ).
6. Reduced Output Impedance: The output impedance of the amplifier with negative feedback is reduced by a factor (1 + Aβ).