A negative feedback amplifier is a type of electronic amplifier circuit that uses negative feedback to improve stability and linearity. It works by taking a portion of the output signal and feeding it back in opposite phase (i.e., negative feedback) to the input of the amplifier. This technique has several benefits that contribute to improved stability and linearity:
Reduces gain: Negative feedback reduces the overall gain of the amplifier. A high-gain amplifier can be prone to oscillations or instability due to parasitic capacitance, inductance, or other reactive elements in the circuit. By reducing the overall gain, the negative feedback helps stabilize the amplifier, preventing unwanted oscillations.
Decreases sensitivity to component variations: Components in electronic circuits can have manufacturing tolerances, which may lead to variations in their values. A negative feedback amplifier tends to be less sensitive to these component variations, as the feedback compensates for changes in the amplifier's characteristics.
Linearizes the transfer function: The negative feedback alters the transfer function of the amplifier to make it more linear. Nonlinear distortion in amplifiers can introduce harmonic components in the output signal that were not present in the input signal. By providing feedback that counteracts these nonlinearities, the amplifier's output becomes more faithful to the input signal, resulting in better linearity.
Reduces higher-order distortions: Some amplifiers can produce higher-order distortions (e.g., third-order, fifth-order) that can affect the linearity of the output signal. Negative feedback tends to reduce these higher-order distortions, further improving linearity.
Lowers output impedance: Negative feedback typically reduces the output impedance of the amplifier. This means the amplifier can drive loads (such as speakers or other circuits) more effectively without significant loss of signal due to internal resistance. A lower output impedance enhances the linearity and stability of the amplifier in various operating conditions.
Minimizes thermal effects: Negative feedback can help compensate for thermal effects that can cause changes in the amplifier's characteristics due to temperature variations. This thermal compensation enhances the stability and performance of the amplifier over a range of operating temperatures.
In summary, a negative feedback amplifier improves stability and linearity by reducing gain, compensating for component variations, linearizing the transfer function, reducing higher-order distortions, lowering output impedance, and minimizing the impact of thermal effects. It is a widely used technique to achieve reliable and accurate amplification in a wide range of electronic systems.