Briefly describe the impact of negative feedback on amplifier circuit performance

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

Briefly describe the impact of negative feedback on amplifier circuit performance

Posted Date: 2024-01-22

Negative feedback in an amplifier circuit refers to the introduction of a feedback loop in the amplifier circuit to feed back part of the output signal to the input end of the circuit. This feedback signal is combined with the input signal to control and adjust the working state and gain of the circuit to achieve the purpose of improving circuit performance and making the output signal closer to the desired signal.

Negative feedback gets its name from the fact that the feedback signal acts in the opposite direction to the output signal. Typically, negative feedback reduces the amplification of a circuit by reducing the difference between the input signal and the output signal. This can improve the linearity of the circuit, reduce nonlinear distortion, and stabilize the operating point and frequency response of the amplifier circuit. At the same time, negative feedback can also reduce the interference of the circuit on the external environment and improve the anti-interference ability of the system.

Through negative feedback, the gain, frequency response, distortion characteristics, etc. of the circuit can be controlled, making the amplifier circuit more stable and reliable, and the output signal more accurate and controllable. This technology is widely used in various amplification circuits, such as amplifiers, operational amplifiers, etc., to meet the requirements of different applications.

Negative feedback circuit analysis method

Negative feedback circuit is one of the more difficult circuits for beginners to learn. If you master the basic circuit analysis method, learning will be easier.

1. Instantaneous signal polarity analysis method

There is a specific method for analyzing the working principle of negative feedback circuits, that is, the instantaneous polarity analysis method of signal voltage is used. As shown in the figure is a negative feedback circuit. This circuit is used as an example to introduce this circuit analysis method.

2. Circuit analysis instructions

When analyzing negative feedback circuits using the instantaneous signal polarity analysis method, the following points should be noted.

3. Analysis and explanation of negative feedback signal types

When analyzing a negative feedback circuit, it is necessary to analyze the type of signal participating in negative feedback, such as a DC signal or an AC signal, for an AC signal, whether it is a low-frequency or high-frequency signal, or a signal of a specific frequency.

When analyzing the types of signals participating in negative feedback, we mainly look at the characteristics of the negative feedback circuit and the characteristics of the entire negative feedback loop. These loop characteristics determine the type of negative feedback.

Negative feedback can have a variety of effects on amplifier circuit performance. Here are some of them:

1. Reduce nonlinear distortion: Negative feedback can reduce the nonlinear distortion of the amplifier circuit. By introducing a feedback signal, part of the output signal is offset or compensated for the input signal, making the output signal closer to the desired input signal. This can reduce nonlinear distortion and improve the linearity and accuracy of the circuit.

2. Improve stability: Negative feedback can increase the stability of the amplifier circuit. When external factors (such as temperature changes, component parameter drift, etc.) cause changes in the circuit operating point, negative feedback will adjust the output signal to offset these changes to maintain the stability of the amplifier circuit.

3. Control gain: Negative feedback can control the gain of the amplifier circuit by adjusting the amplitude of the feedback signal. Through appropriate feedback network design, precise gain control can be achieved so that the amplification factor of the output signal meets actual needs.

4. Extended frequency response: Negative feedback can expand the frequency response range of the amplifier circuit through appropriate feedback network design. For example, clamping negative feedback can reduce the corresponding bandwidth of the amplifier circuit, allowing it to transmit higher frequency signals, and also has a better amplification effect on low-frequency signals.

5. Adjust input/output impedance: Negative feedback can adjust the input and output impedance of the amplifier circuit through the design of the feedback network to adapt to the characteristic matching of different signal sources and loads, and improve the efficiency and quality of signal transmission.

Negative feedback may also introduce some negative effects, such as introducing noise gain, limiting the bandwidth of the circuit, etc. Therefore, when designing and applying negative feedback, it is necessary to comprehensively consider various factors and balance performance indicators and constraints to achieve optimal amplifier circuit performance.

Review Editor: Huang Fei

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