Introducing negative feedback with an integrator as the central element

Negative feedback is introduced using an integrator as the central element by making intuitive connections with the way we sense the difference between desired and actual values and continuously adjust the latter so that it reaches the desired value. In contrast to the traditional use of a memoryless high gain amplifier as the central element, this approach makes it clear right from the beginning that negative feedback circuits take time to respond (have a finite bandwidth), that some excess delay can be tolerated, while larger excess delays lead to ringing and eventually instability, and that negative feedback circuits can be stabilized by slowing them down. Time domain intuition and analysis lead to key conclusions regarding the stability margin of negative feedback circuits. This approach complements the conventional frequency domain approach by serving as an introduction that anticipates the results that are derived by the latter. The presented approach also lends itself better to synthesis of key negative feedback blocks such as opamps and the phase locked loop. © 2012 IEEE.