Voltage Amplifier 72 on GRE: Negative Feedback Effects

[yxgao]

72 on GRE. In a voltage amplifier, which is the following is NOT usually a result of introducing negative feedback?
a. Increased amplification
b. Increased bandwidth
c. Increased stability
d. decreased distortion
e. decreased voltage gain

The answer is A. Can someone explain what happens in general during negative feedback. b-e are obviously true, but can someone explain the complete reasoning behind it?

 

[chroot]

https://www.physicsforums.com/showthread.php?s=&threadid=8341

- Warren

 

[M98Ranger]

Negative feedback is a technique used in electronic circuits to reduce the output signal of an amplifier, thus providing a more stable and accurate output. This is achieved by feeding a portion of the output signal back to the input of the amplifier in a way that it opposes the input signal. This results in a decrease in the overall gain of the amplifier.

In general, negative feedback has the following effects on a voltage amplifier:

b. Increased bandwidth: By reducing the overall gain of the amplifier, negative feedback also reduces the amount of distortion and noise in the output signal. This allows for a wider frequency range to be amplified, resulting in increased bandwidth.

c. Increased stability: Negative feedback also helps to stabilize the output of the amplifier by reducing the effects of variations in the input signal and changes in the components of the amplifier. This results in a more stable and reliable output.

d. Decreased distortion: As mentioned earlier, negative feedback reduces the amount of distortion in the output signal. This is because the feedback signal helps to cancel out any nonlinearities in the amplifier, resulting in a more accurate output signal.

e. Decreased voltage gain: This is the most significant effect of negative feedback. As the feedback signal reduces the overall gain of the amplifier, the voltage gain is decreased. This means that the output signal will be smaller than the input signal, but it will be more stable and accurate.

So, in summary, negative feedback has the overall effect of reducing the amplification of the input signal while improving the stability, bandwidth, and distortion characteristics of the amplifier. This is why negative feedback is an important technique in voltage amplifiers.