Feedback is the process of comparing the actual output response of a system to a desired output, typically derived from a reference value, in order to achieve a balance. It can be likened to a mass beam scale, where the aim is to find a specific weight by adding or removing weights on one side until the beam becomes horizontal. However, the weights of the added pennies may not exactly equal the desired weight, necessitating the act of continuously adding or removing pennies to maintain the balance of the beam scale. This iterative process exemplifies the essence of a feedback system.
Negative feedback aims to minimize the difference between the output and the reference. In the aforementioned example, the act of balancing the pennies to achieve a weight of 500 mg represents negative feedback, as it ensures the weight beam remains stable and level.
In contrast, positive feedback seeks to maximize the difference between the output and the reference. Using the same example, if the process of adding or removing pennies on the scale is not sufficiently fast, the beam will tilt to one side and become unstable, illustrating the consequences of positive feedback.
Feedback plays a critical role in maintaining system stability. The majority of designs employ negative feedback to regulate the output and maintain it at the reference value. However, disturbances and limited bandwidth can disrupt the balance of the system and render the output unstable, often resulting in large oscillatory responses. Thus, understanding and implementing appropriate feedback mechanisms are essential for achieving stability in various systems and mitigating undesired effects.