Negative feedback is a concept used in electronics and control systems, where a portion of the output signal is fed back to the input with an inverted polarity to reduce the overall gain of the system. It is commonly used in amplifiers to improve their performance, stability, linearity, and reduce distortion.
In an amplifier with negative feedback, a part of the output signal is combined with the input signal, but it is phase-inverted (180 degrees out of phase) before being applied to the input again. This effectively reduces the effective gain of the amplifier.
Here's how negative feedback impacts amplifier performance:
Reduced distortion: Negative feedback helps in reducing distortion in the output signal of the amplifier. By reducing the gain, the amplifier operates more linearly, which results in a more faithful reproduction of the input signal.
Improved frequency response: Negative feedback can extend the bandwidth of an amplifier, making it more responsive across a wider range of frequencies.
Increased stability: Amplifiers with negative feedback are generally more stable than those without it. The feedback helps to suppress any parasitic oscillations or unwanted behavior that may occur due to complex interactions between the internal components of the amplifier.
Lower output impedance: Negative feedback can reduce the output impedance of the amplifier, which leads to better impedance matching and allows the amplifier to drive a wider range of loads effectively.
Reduced noise: In some cases, negative feedback can help in reducing noise and improve the signal-to-noise ratio of the amplifier.
Trade-offs: While negative feedback offers several advantages, it also introduces some trade-offs. Excessive negative feedback can reduce the overall gain too much, leading to reduced sensitivity. Additionally, it may introduce phase shifts that affect the phase response of the amplifier.
Designing an amplifier with the right amount of negative feedback is a delicate balancing act to achieve the desired performance characteristics while minimizing potential drawbacks. Amplifier designers carefully analyze the application requirements and the specific trade-offs to optimize the overall performance of the amplifier.