
Feedback Circuit Techniques
Lecturer: Kent Lundberg
All electronic systems employ feedback. All analog circuits,
including op amps, oscillators, filters, and power supplies
(just to name a few), critically depend on feedback. Some of
these feedback loops are explicit, some are implicit, some are
intentional, and some are unintentional. In all cases, the
analysis and design of circuits using feedback requires the
knowledge of analytical techniques, creative design, and an
appreciation for possible tradeoffs. Understanding feedback
theory, and its use in practical applications, is the key to
successful system design.
 Introduction to Feedback Circuit Techniques
 Some opamp history
 Simple opamp circuits
 Feedback systems
 Block diagrams
 Desensitivity and Return Ratio
 Benefits of feedback
 Return ratio
 Blackman
 Middlebrook
 Linear System Behavior
 Transfer functions
 The Laplace transform
 Time and frequency response
 Elmore delay
 Feedback Analysis Tools
 Closedloop poles and zeros
 Phase margin
 Nyquist criterion
 Nichols plots
 Rootlocus plots
 Crossover frequency and phase margin
 OpAmp Transfer Function
 Generalpurpose transfer function
 Integrators and differentiators
 Decompensated op amps (OP27 vs. OP37)
 Good generality, bad optimality
 Compensation and Design
 Phase and gain margin
 Gain setting
 Dominant pole
 Lag and lead
 Internal OpAmp Compensation
 Opamp transfer function
 Pole splitting
 Minorloop feedback
 Reducing steadystate errors
 Driving Capacitive Loads
 Gain reduction and overcompensation
 Outoftheloop and intheloop resistance
 Output snubber circuit
 Minorloop compensation
 Current Feedback Amplifiers
 Voltage op amps
 Currentfeedback amps
 Implementation
 Oscillators
 Amplitude control
 Shape
 Limit
 Feedback
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Lecturer
Kent H. Lundberg
is an educator, consultant, and historian. He is president of
Keeling Flight Hardware, Ltd.,
which provides design, research, and educational consulting services in the fields
of aerospace, electronics, and control systems for companies, universities,
and government organizations.
Since 2008, Dr. Lundberg has been a Visiting Professor at
Olin College of Engineering,
where he teaches courses in controls, circuit design, and instrumentation.
From 2002 to 2005 and in 2011, he was a Lecturer with the
Department of Electrical Engineering and Computer Science at the
Massachusetts Institute of Technology.
His research and teaching interests include the application of classical control
theory to problems in analog circuit design, and the development of educational
toys (lecture demos, takehome laboratory kits, and tutorial computer applications)
for feedback systems and control engineering.
Dr. Lundberg was the Associate Editor for History of
IEEE
Control Systems Magazine from 2004 to 2011.
He attended M.I.T. earning a Bachelor's degree in physics in 1992,
and a Ph.D. in electrical engineering in 2002.
He owns 43 Tektronix oscilloscopes, and he obsessivecompulsively
collects analog synthesizers, technology artifacts, and classic textbooks on
radar,
nuclear energy,
analog computing,
and control.
Last updated at 10:11 on Thursday, 10 Jan 2013.
by
Kent Lundberg
