负反馈是控制系统中基本而又重要的一环。负反馈可以使控制系统的过程按一定的轨迹运动，有着广泛的应用。至于正反馈，人们常常联系到不稳定。其实正反馈系统有着非常丰富的内容和应用范围。本文将通过一些例子。论述正反馈系统理论 Negative feedback is a basic but important part of the control system. Negative feedback can control the process of the system by a certain trajectory, has a wide range of applications. As for positive feedback, people are often linked to instability. In fact, the feedback system has a very rich content and application. This article will pass some examples. Discusses the theory of positive feedback system