Table Of ContentINTERMEDIA TE
ELECTRONICS
INTERMEDIATE
ELECTRONICS
R. J. MADDOCK
C. Eng., M.I.E.R.E.
Lecturer in E/ectronics,
Department in Electrical Engineering,
Southampton College of Technology
Book I
Springer Science+Business Media, LLC
ISBN 978-1-4899-5861-7 ISBN 978-1-4899-5859-4 (eBook)
DOI 10.1007/978-1-4899-5859-4
© Springer Science+Business Media New York 1969
Originally published by Butterworth & Co. (Publishers) Ltd. in 1969.
Softcoverreprint of the hardcover Ist edition 1969
Suggested U.D.C. number: 621·37/·38
Library of Congress Catalog Card Nurober 69-18297
PREFACE
Many textbooks adequately cover the development of small signal
equivalent circuits for electronic devices. Students frequently
experience difficulty in applying such circuits to the solution of the
various configurations found in practice. In this volume I have
demonstrated step by step procedures by which the required solutions
may be obtained by the use of such equivalent circuits.
The first chapter shows clearly the necessity for equivalent circuit
methods and also discusses the d.c. biasing requirements and circuits
for valve and transistor amplifiers. A chapter follows covering the
fundamentals of network analysis required for the remainder of the
book. Valve and transistor equivalent circuits are then introduced.
and detailed methods of application are given with many fully
worked examples. Later chapters extend these methods to a dis
cussion on the effects of feedback, the solution of practical feedback
amplifiers and to the analysis and design of a range of sinusoidal
oscillators. A final chapter introduces the modifications required
when considering high frequency operation. The required high
frequency equivalent circuits are given together with sample
calculations.
I have included worked solutions and problems with answers in
all chapters. The parameters chosen for the various equivalent
circuits are those most commonly available from manufacturers'
published data. British Standard symbols and units are used through
out except where very recent changes may be unfamiliar to the
majority of students.
Both valve and transistor circuits are discussed as I feel that for
many students the valve provides a useful teaching medium, but
in the later chapters, the stress is, in general, on transistor circuits.
The physical operation of the devices has not been covered, as
adequate Iiterature is available elsewhere. A list of works for further
reading is provided at the end of the book.
I have written this book as a result ofthe experience gained through
teaching students at Higher National Diploma and Certificate level
but I feel that it should also be useful for students at the early stages
of degree courses and the final year of technician courses.
V
PREFACE
I would like to offer my thanks to those members of the staff and
students of Southampton College of Technology who have helped
in the preparation of this book and to Miss L. Lavender and Mrs. R.
Huntingford for their assistance in typing the manuscript.
R. M.
vi
CONTENTS
Preface v
1. Graphical Analysis of Electronic Circuits . 1
2. Fundamentals of Network Analysis . 42
3. Low Frequency, Small Signal Equivalent Circuits for Valves
and Transistors . 94
4. Use of the Valve Equivalent Circuit. 112
5. Use of Transistor Equivalent Circuits 140
6. The Theory of Feedback Amplifiers. 181
7. Practical Feedback Amplifiers . 220
8. Oscillators 255
9. Modifications to Equivalent Circuits for High Frequency
Operation . 291
Appendix 1. Use of Logarithmic Units 312
Works for Further Reading 315
Index 317
vii
1
GRAPHICAL ANALYSIS OF
ELECTRONIC CIRCUITS
Electronic engineering is principally concerned with the behaviour of
electrical circuits or networks containing various non-linear and
active devices. These include the various types of rectifier, thermionic
valves, transistors, transducers such as photocells and many other
devices. The difficulty in designing or analysing such circuits lies
in their inherent non-linearity. The physical explanation of their
behaviour will not in general be discussed in this book since this
aspect is more than adequately covered by other authors.
We must first consider suitable methods of describing the behaviour
of a particular device. Any chosen description will be suitable only
for a limited set of conditions. This concept is not peculiar to these
electronic devices; a capacitor, for example, may be shown as a pure
capacitance shunted by a resistance representing the dielectric loss.
This representation holds only if the peak voltage does not exceed
the breakdown value for the capacitor. Also large changes in tem
perature or humidity may well affect this model.
D.C. CHARACTERISTICS
The first description ofvalves and transistors that will be considered
are the so-called d.c. characteristics. These characteristics are graphs
showing how the various direct voltages applied to the device
+I
-V
(a) (b)
-I
Figure 1.1. The characteristics of a resistor
GRAPHICAL ANALYSIS OF ELECTRONIC CIRCUITS
change the direct currents ftowing in it. lf there are more than two
variables, the values of one are plotted as a second is changed
with all others held constant. A variable that is fixed is known as a
parameter of the characteristics. A simple example of this would be
the variation of current ftowing in a resistor with variation of applied
voltage. In this case the parameter could be the ambient temperature.
The resulting family of characteristics are shown in Figure 1.1.
Similarly with thermionic and semiconductor diodes the cathode
and ambient temperature respectively could be taken as the para
meters, as shown in Figure 1.2a and b.
-[ fa=40°C
t1 = 7oooc ta=20°C
,___ _ 650°C
6QQ°C
-V +V -Vv =;z=::;:=~---:;+ V
ta= 20°C
-I fa=f.QOC
(a) (b) -I
Figure !.2. Diode characteristics. (a) Thermionic. (b) p-n junction
With three-electrode devices such as triode valves and transistors
the cathode or ambient temperatures are assumed to be constant
and the parameters of the characteristics are taken as one of the
applied voltages or currents. For example the anode characteristics
of a triode valve are shown with constant cathode temperature
(filament voltage), while the anode current (h), is measured for
different values of anode--cathode voltage (VAK) taking the grid
cathode voltage (VGK) as the parameter. A 'family' of characteristics
is thus obtained for different fixed values of VGK (Figure 1.3a).
For the transistor collector characteristics, the ambient temperature
is constant thus collector current (/c) is plotted against the collector
emitter voltage (VcE) using the base current (/B) as the parameter
(Figure 1.3b).
With multi-electrode devices such as pentode valves, other
potentials or currents will have to be kept constant for a particular
set of characteristics. The anode characteristics of a pentode are
quoted for constant filament voltage (VF) constant screen voltage
(VG2K) and constant suppressor cathode voltage (VGaK). The para
meter again is VGlK·
2
D.C. CHARACTERISTICS
<l: 10
E
~5
OIJ.A
5 10 15
VcE· volts
(a) (b)
Figure 1.3. Active device characteristics. (a) Triode valve. (b)
Common emitter transistor
D.C. Operating Point
The operating point is given by the values of the two variables
and the parameter corresponding to a particular point on the
characteristics. Since these three variables are not independent, the
operating point is completely defined by any two of the three.
For example a particular operating point for a triode valve could
be given as VAK 150 V, h 3 mA, or h 3 mA, VaK-2 V, or as
VAK 150 V, VaK-2 V (see Figure 1.4a). Foratransistor it might be
VcE• volts
(a) (b)
Figure 1.4. Permissihle range of d.c. operating point for (a) triode
valve and (b) transistor
given by Ic 2 mA, h 50 flA or Ic 2 mA, VcE 3 V etc. (Figure 1.4b).
The operating point can lie anywhere within the range given by the
characteristics. In practice it should not lie outside the shaded area
shown, since no information is given in the particular set of character
istics. Thus we can say the characteristics provide one restriction
3
