Negative feedback is a technique used in amplifiers to improve their performance by reducing distortion and improving linearity. It involves feeding a portion of the output signal back to the input in a way that opposes the original input signal. This helps in reducing the overall gain of the amplifier and improving various performance parameters. However, it is important to note that negative feedback does not enhance all performance parameters of an amplifier equally.

Gain:
- Negative feedback reduces the overall gain of the amplifier. It achieves this by feeding a portion of the output signal back to the input in a way that opposes the original input signal. This effectively reduces the gain of the amplifier and helps in maintaining stability.

3-dB Noise:
- The 3-dB noise bandwidth is a measure of the noise power in the frequency range over which the signal power is reduced by 3 dB. Negative feedback does not have a significant impact on the noise performance of an amplifier. The noise introduced by the amplifier's components and circuitry remains largely unaffected by negative feedback.

Noise Figure:
- The noise figure is a measure of how much the amplifier degrades the signal-to-noise ratio of the input signal. Negative feedback can help in reducing the noise figure of an amplifier. By reducing distortion and improving linearity, negative feedback helps in minimizing the impact of noise introduced by the amplifier's components and circuitry.

Input Impedance:
- Negative feedback does not have a significant impact on the input impedance of an amplifier. The input impedance is primarily determined by the amplifier's input circuitry and is not significantly affected by the application of negative feedback.

In summary, negative feedback enhances the performance parameters of an amplifier by reducing distortion, improving linearity, and minimizing the impact of noise. However, it does not enhance the gain or input impedance of the amplifier.