EBOOK - Designing Dynamic Circuit Response (Analog Circuit Design 2) (Dennis Feucht)

Solid-state electronics has been a familiar technology for almost a half century, yet some circuit ideas, like the transresistance method of finding amplifi er gain or identifying resonances above an amplifi er’s bandwidth that cause spurious oscillations, are so simple and intuitively appealing that it is a wonder they are not better understood in the industry.
I was blessed to have encountered them in my earlier days at Tektronix but have not found them in engineering textbooks. My motivation in writing this book, which began in the late 1980s and saw its fi rst publication in the form of a single volume published by Academic Press in 1990, has been to reduce the concepts of analog electronics as I know them to their simplest, most obvious form, which can be easily remembered and applied, even quantitatively, with minimal effort.
The behavior of most circuits is determined most easily by computer simulation. What circuit simulators do not provide is knowledge of what to compute.

The creative aspect of circuit design and analysis must be performed by the circuit designer, and this aspect of design is emphasized here. Two kinds of reasoning seem to be most closely related to creative circuit intuition:
1. Geometric reasoning: A kind of visual or graphic reasoning that applies to the topology (component interconnection) of circuit diagrams and to graphs such as reactance plots.
2. Causal reasoning: The kind of reasoning that most appeals to our sense of understanding of mechanisms and sequences of events. When we can trace a chain of causes for circuit behavior, we feel we understand how the circuit works.

Chapter 1  Transient and Frequency Response . . . . . . . . . . . . . . . . . . . . . . .  1
Reactive Circuit Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
First-Order Time-Domain Transient Response . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Complex Poles and the Complex Frequency Domain . . . . . . . . . . . . . . . . . . . . 7
Second-Order Time-Domain Response: RLC Circuit . . . . . . . . . . . . . . . . . . . . 10
Forced Response and Transfer Functions in the s-Domain . . . . . . . . . . . . . . . 16
The Laplace Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Time-Domain Response to a Unit Step Function . . . . . . . . . . . . . . . . . . . . . . . 29
Circuit Characterization in the Time Domain. . . . . . . . . . . . . . . . . . . . . . . . . . 37
Thes-Plane Frequency Response of Transfer Functions . . . . . . . . . . . . . . . . . 41
Graphical Representation of Frequency Response . . . . . . . . . . . . . . . . . . . . . . 43
Loci of Quadratic Poles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Optimization of Time-Domain and Frequency-Domain Response . . . . . . . . . 53
Reactance Chart Transfer Functions of Passive Circuits . . . . . . . . . . . . . . . . . . 61
Closure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Chapter 2  Dynamic Response Compensation . . . . . . . . . . . . . . . . . . . . . . .  75
Passive Compensation: Voltage Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Op-Amp Transfer Functions from Reactance Charts . . . . . . . . . . . . . . . . . . . . 78
Feedback Circuit Response Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Feedback Circuit Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Compensation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Compensator Design: Compensating with Zeros in H. . . . . . . . . . . . . . . . . . 105
Compensator Design: Reducing Static Loop Gain . . . . . . . . . . . . . . . . . . . . . 118
Compensator Design: Pole Separation and Parameter Variation . . . . . . . . . 120
Two-Pole Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Output Load Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Complex Pole Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Compensation by the Direct (Truxal’s) Method . . . . . . . . . . . . . . . . . . . . . . . 162
Power Supply Bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Chapter 3  High-Frequency Impedance Transformations . . . . . . . . . . . . . .167
Active Device Behavior above Bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
BJT High-Frequency Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Impedance Transformations in the High-Frequency Region. . . . . . . . . . . . . 170
Reactance Chart Representation of b-Gyrated Circuits. . . . . . . . . . . . . . . . . . 177