Why Feedback Resistor Should Not Be Too Large Feedback resistors play a crucial role in electronic circuits. They improve amplifier performance, enhance stability, and reduce nonlinear distortion. However, excessively large feedback resistors can negatively impact circuit performance and stability. Below, we will discuss in detail why feedback resistors should not be too large.
First, excessively large feedback resistors affect the amplifier's gain. In a feedback circuit, increasing the feedback resistor leads to an increase in feedback current, thus reducing the amplifier's gain. This is because the feedback resistor's function is to re-input the amplifier's input signal through the feedback loop, mixing it with the input signal to form a new input signal, thereby reducing the difference between the output and input signals. If the feedback resistor is too large, the feedback current will alter the ratio between the input and output voltages, further reducing the amplifier's gain. Therefore, a suitable feedback resistor should be selected to ensure the effectiveness of the feedback circuit while maintaining the amplifier's full-frequency response and avoiding excessive attenuation.
Second, excessively large feedback resistors affect the amplifier's bandwidth. Excessive feedback resistance can distort the voltage and current signals in the feedback loop, resulting in a reduced amplifier bandwidth. This is because an excessively large feedback resistor can render the signal in the feedback loop meaningless or weak, affecting the amplifier's output. Therefore, the amplifier's bandwidth characteristics should be considered during circuit design to avoid signal distortion or amplifier instability caused by excessive feedback resistance.
Furthermore, excessive feedback resistance can increase output distortion. Distortion refers to a significant difference between the output and input signals, which the feedback circuit aims to reduce. However, if the feedback resistor is too large, excessive feedback current will fill the circuit, affecting the amplifier's output and increasing signal distortion. Therefore, properly adjusting the feedback resistor value is crucial for maintaining the overall performance of the amplifier circuit.
Finally, excessive feedback resistance can also affect the amplifier's stability. The characteristic of a feedback circuit is to feed the output signal back to the amplifier's input, adjusting the amplification by changing the total input voltage. However, excessive feedback resistance can cause circuit instability because excessive feedback attenuation not only makes the output signal unstable but also makes it difficult to adjust the power amplifier's current and output resistance. Therefore, when selecting the size of the feedback resistor, the overall stability of the circuit must be considered to ensure its overall performance.
In summary, the feedback resistor should not be too large, as an excessively large feedback resistor will severely affect the circuit's performance and stability. When designing a circuit, the size of the feedback resistor should be considered from multiple perspectives to ultimately select a suitable one, ensuring the circuit's effectiveness and performance stability. By rationally selecting the feedback resistor, the circuit's performance and stability can be effectively improved, ensuring its normal operation and providing a fundamental guarantee for circuit optimization and functionality.
