Negative feedback is a fundamental concept in electronics and control systems. It refers to a process where a portion of the output signal from a system is fed back and combined with the input signal in such a way that it reduces the overall gain or amplification of the system. The result is a more stable and controlled operation of the system.
The principle of negative feedback can be understood by looking at its main components:
Input Signal: The original signal or information that needs to be amplified or processed. In the case of an amplifier circuit, this is the input voltage or current that requires amplification.
Amplifier: The component responsible for boosting the input signal to a larger magnitude. This could be a simple transistor-based amplifier or a more complex operational amplifier (op-amp).
Feedback Path: This is the connection that feeds back a portion of the output signal to be combined with the input. It creates a feedback loop.
Summing Point: The point in the circuit where the input and feedback signals are combined.
Output Signal: The amplified signal that is the final result of the process.
Now, let's see how negative feedback works in an amplifier circuit:
Initially, the input signal is applied to the amplifier, which then produces an amplified output signal.
The output signal is connected to a feedback network, which attenuates the signal and returns a fraction of it back to the summing point. The feedback network can be a simple resistor network or a more complex combination of components.
At the summing point, the original input signal and the feedback signal are combined. The feedback signal opposes the input signal, creating a negative feedback effect.
This negative feedback reduces the overall gain of the amplifier. As the output signal increases due to the amplification, the feedback signal increases as well, opposing the input signal and limiting further amplification.
Applications of Negative Feedback in Amplifier Circuits:
Improved Linearity: Negative feedback improves the linearity of the amplifier by reducing distortion and nonlinearities, resulting in a more accurate representation of the input signal in the output.
Increased Stability: Negative feedback stabilizes the amplifier's operation by reducing sensitivity to changes in component parameters and temperature variations. This helps prevent thermal drift and other instabilities.
Wider Bandwidth: By reducing the gain at higher frequencies, negative feedback can extend the bandwidth of an amplifier, allowing it to handle a broader range of frequencies.
Reduced Noise: Negative feedback can help decrease noise in the output signal since it attenuates the noise components introduced by the amplifier.
Lower Output Impedance: Negative feedback decreases the output impedance of the amplifier, making it easier to drive low impedance loads.
Overall, negative feedback is a powerful tool in amplifier circuits, helping to achieve desirable performance characteristics, improve stability, and enhance linearity, making it a vital technique in various electronic systems and applications.