Massachusetts Institute of Technology
Department of Electrical Engineering

Feedback Systems

Spring 2012


Feedback Systems is quite possibly the most important class you will ever take. Everything needs feedback. You will never design an electronic or an electromechanical system that does not include a feedback loop, either explicitly or implicitly.

Every interface to the real world --- whether you are building a robot arm, a temperature control system, an audio power amp, or an RF synthesizer (the list goes on and on) --- needs to drive some kind of actuator --- a motor, a heater, a power transistor, or an oscillator. To make sure that actuator is doing the right thing, you need to measure the output (its position, its temperature, its voltage, or its frequency) and compare that measurement to what you meant to do. In other words, you need feedback.

Course Content

Introduction to design of feedback systems. Properties and advantages of feedback systems. Time-domain and frequency-domain performance measures. Stability and degree of stability. Root locus method. Nyquist criterion. Frequency-domain design. Compensation techniques. Application to a wide variety of physical systems. Internal and external compensation of operational amplifiers. Modelling and compensation of power coverter systems. Phase lock loops.


You will have four short lab projects and a design problem to do --- about one every other week --- ranging in subject from operational amplifiers to thermal systems. We hope you find these labs illustrative and informative.

We start the term by studying a servomotor mechanism. There are many good reasons for using motors in these four labs (labs 1A, 1B, 1C, and 1D). Most of all, we believe that it is a valuable experience. In your careers as engineers, the systems you design and build will often interface to the real world with motors, actuators, and sensors of all kinds. We believe that these labs are an excellent introduction to this kind of design.

In the design problem you will have a choice among several projects.

Prerequisites: 6.003 or 2.003 or 16.040

The prerequisites for 6.302 are linear systems, circuits, physics, and math. Officially, this requirement is 6.003 or 2.003 or 16.040. Previous laboratory experience with circuits is assumed, such as in 6.002 or 6.071 or 16.040. We also assume that you have not forgotten 8.01 or 8.02, and that you have had some exposure to complex variables (18.04 is helpful, but overkill).

Course Reference

The reference for this course will be Kent Lundberg's Notes on Feedback Systems. These notes will be handed out in lecture. For up-to-date information, errata, and supplementary material, please visit the notes webpage.

Java Demos and iLab

These demos have been written under the supervision of Dr. Kent Lundberg. On Athena, you need to use Mozilla to have the correct Java plugin.

Other Links

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Last updated: $Date: 2012-02-08 10:09:58 -0500 (Wed, 08 Feb 2012) $ by $Author: tbarton $