Feedback loop

The mechanism that connects the output of a system or a subsystem to its input. Sometimes used as a synonym for feedback. A positive feedback loop is one in which an output signal amplifies the input; this moves the system away from stability. A negative feedback loop is one in which an output signal is of opposite polarity to the input; this arrangement tends to move the system toward stability. The path of feedback may be non-linear and shaped by filters, amplifiers, or electronic (as in a resistive/ capacitive filter) or mechanical components (as in a mechanical governor). Feedback loops are used in almost all control systems; the term is used in mechanics, modeling and analysis of dynamic systems, and in automatic control systems such as autopilots and air conditioning.