Electronic Components, Tubes and Transistors

170 Pages·1965·3.021 MB·English

by  G. W. A. Dummer and N. Hiller (Auth.)

Electronic Components
Tubes and Transistors
BY
G. W. A. DUMMER
M.B.E., M.I.E.E., SEN. MEM. I.E.E., M.I.E.R.E.
PERGAMON PRESS
OXFORD • LONDON • EDINBURGH • NEW YORK
PARIS • FRANKFURT
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Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1
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Copyright © 1965
Pergamon Press Ltd.
Library of Congress Catalog Card No. 65-19841
First edition 1965
Set in Times 10 on 12 pt
and Printed in Great Britain
by Blackie and Son Ltd., Glasgow
This book is sold subject to the condition that
it shall not, by way of trade, be lent, resold,
hired out, or otherwise disposed of without the
publisher's consent, in any form of binding or
cover other than that in which it is published.
Preface
COMPONENT parts are the building blocks of all electronic equip-
ments. This book is intended to bridge the gap between basic
measurement theory of resistance, capacitance and inductance
and the practical application of electronic components in equip-
ments. Basic theory of electron tubes and semiconductors is
available in other textbooks and the more practical, or usage,
aspect is dealt with in this volume.
Experience in the correct choice of a component, tube or
transistor is difficult to achieve and incorrect use of these devices
may result in expensive repairs. The reliability of complex
electronic equipments depends a great deal on the choice and
correct use of the individual component parts. The essential
characteristics of each main type of component, tube and tran-
sistor are therefore summarized and references given for further
reading if desired.
It is hoped that this book will help the student over the difficult
problem of choosing the right component and device for his
particular application.
G. W. A. DUMMER
Acknowledgements
THE author would like to acknowledge the help and valuable
comments of Mr. C. H. Miller, Dr. J. W. Granville, Mr. M. W.
Foulkes-Roberts, Mr. W. T. Blackband, Mr. D. E. H. Jones and
Mr. P. Lloyd in the preparation of this book. The valuable
advice of Mr. W. Hickson of the College of Electronics, Malvern,
on the requirements of modern students and particularly in the
preparation of the questions, is specially acknowledged.
The author would also acknowledge the co-operation of
Messrs. Sir Isaac Pitman & Sons in allowing certain material
from the "Radio and Electronic Components" series on com-
ponents to be summarized in this book.
Acknowledgement is also made to Messrs. Standard Telephones
and Cables Ltd. for permission to use data from their Components
News, also the Mullard Co. and all other firms who have provided
drawings of components.
The views expressed in this book are those of the author and
do not necessarily represent the views of the Ministry of Aviation.
CHAPTER ONE
Fixed and Variable Resistors
Fixed Resistors
Resistors are generally available in one of two categories—high-
stability or general-purpose. High-stability types include the
pyrolytic or cracked-carbon resistors, the wirewound resistors
and the metal or metal-oxide film resistors, all of which are
capable of providing stable resistance to within 1 or 2 per cent.
General-purpose types are usually of carbon composition and are
cheaper and usually smaller. There are two methods of manu-
facture of carbon composition resistors—the solid rod con-
struction shown in Fig. 1.1 and the film construction shown in
Fig. 1.2. They are not so stable, and resistance variations on load
may be from 5 to 20 per cent. The characteristics of the individual
types of resistor vary widely, and it is necessary to know these
variations before a choice can be made of the correct resistor for
any particular application. The essential characteristics are
summarized in terms of the parameters usually required in
choosing a resistor.
Size
In general, carbon resistors dissipate less power than wire-
wound resistors of the same resistance value, and are smaller.
The maximum resistance of a wirewound resistor is limited by the
length of wire of a given material and diameter which can be
wound upon the available former length. Subminiature cracked-
2 ELECTRONIC COMPONENTS, TUBES AND TRANSISTORS
Sprayed Metal Solder
Paint Coatinfi
Contact
Resistive
Carbon
Composition
- End m
Connection
> Uninsulated types
Resistive Carbon Composition r-Paint Coating
' a| Embedded
^[Connection
,— Embedded
j£) Connection
Wire
Moulded
Thermosetting
Plastic Cover
End Cap, Insulated types
(Force fit
on Rod)
Tube
Resistive Carbon
Composition Rod Ends of Rod Metal-sprayed
FIG. 1.1. Carbon composition {solid rod) types.
carbon high-stability resistors are made which are comparable in
size with the carbon composition type, which may be as small as
To in. diameter and \ in. long.
Metal and oxide film resistors are usually larger for high
resistance values because of their lower (ohms/square) resistivity.
uoe—, r— Plastic Moulding
' "■." -. " k A »v " r~"s ~" —F—* < ^ V "VN End
Connection
J— . Conducting
Cement
Rcsisttve_ Wire Termination Inserted
Coating
Inside Tube to Conduct Away Heat
FIG. 1.2. Carbon composition film type.
FIXED AND VARIABLE RESISTORS 3
Power-handling Capacity
Composition resistors are commonly available for dissipating
up to about 2 W, but rarely over 5 W (except in special resistors
of low ohmic values). Cracked-carbon resistors (see Fig. 1.3 for
Silicon Cracked-carbon
Lacquer Film
Coating
Spiralled Colloidal Ceramic
Track Graph He Hod
FIG. 1.3. Cracked-carbon film (pyrolytic) type.
construction) are available up to 2 W at normal temperatures.
All these ratings have to be reduced when the resistors are used
at high ambient temperatures. Small metal film resistors (see
Fig. 1.4) are made up to 2 W dissipation and small oxide film
FIG. 1.4. Metal film (nickel-chromium) types.
resistors up to 6 W dissipation. Wirewound resistors (see Fig. 1.5)
are invariably used when higher powers are to be dissipated, and
some vitreous-enamelled wirewound types will handle powers as
great as 300-400 W (see Fig. 1.6). Large oxide and metal film
resistors are made also to dissipate several hundred watts. It is
important to remember that the temperatures reached by the
4 ELECTRONIC COMPONENTS, TUBES AND TRANSISTORS
Wire-wound
Moulded
resistance element
Resin
Leads crimped
to element
FIG. 1.5. Wirewound general-purpose {moulded) type.
Nickel- Chrome Wire Tinned Copper
Welded to Resistance Wire Soldered
Wire and Brazed to to End Cap
End Cap Nickel-Chromium
End Cap or Nickel- Copper
3. r—Resistance Winding
Ceramic Vitreous
Tube Former Enamel Coating
Brazed Connection to
Nickel- Chrome Anchor Winding
Ceramic -Resistance Vitreous
lube Wire Enamel Coating
Wire
Winding
Ceramic y Vitreous n Alternative
Tube / Enamel Coating
End m
Connection
FIG. 1.6. Wirewound general-purpose {vitreous-enamelled) types.
FIXED AND VARIABLE RESISTORS 5
resistors when dissipating these wattages can be very high—of
the order of several hundred degrees Centigrade.
There is a "critical value" of resistors for each wattage rating,
v2
given by R =— , at which the maximum voltage is applied for the
w
given wattage.
In pulse operation (particularly when the duty cycle is low) only
the mean power is effective in raising the internal temperature of a
resistor. As the power is supplied in short pulses, very high peak
ratings are possible, but the mean power should not exceed the
continuous rating wattage. Peak pulse voltages for high-stability
(cracked-carbon) resistors should be limited to twice the normal
rated d.c. voltage, otherwise the limit set by internal sparking or
external corona might be exceeded, while for general-purpose
carbon composition resistors, the maximum peak pulse voltage
should be no greater than the maximum continuous rating.
Stability
Stability and accuracy are often confused. Stability is the
change in resistance under shelf life or working conditions;
accuracy is the tolerance to which the value of the resistor is made
or selected. For general purposes, the carbon composition type
has been used for many years and is therefore known to have an
acceptable long-term stability for domestic and many commercial
purposes. Changes in resistance under normal working conditions
may be of the order of 5 per cent, but in more severe conditions,
such as those encountered in the Services, changes of up to 25
per cent may occur. It is found that changes caused by high
temperature (due either to ambient or self-generated heat) result
in a permanent increase in resistance value, while exposure to high
humidity increases the resistance, but the effect is largely reversible.
The stability of wirewound and cracked-carbon resistors is
much higher—of the order of 1-2 per cent. Metal film resistors
are comparable in stability to the wirewound types. This
6 ELECTRONIC COMPONENTS, TUBES AND TRANSISTORS
stability is dependent mainly on the protection afforded to the
resistive element by sealing. Even under the severe conditions
encountered in the Services, changes are not usually more than
2 per cent. Oxide films have a stability rather better than that of
the cracked-carbon film.
Rubberized Wound with
End Cap Nickel - chrome
Tube Insulated or Copper-nickel Brass Tube,
Internally with- l Enamelled Wire St&nnate Tinned
Oiled Paper
20SWG Sleeving
TC Wire * over
Connections
Ceramic Insulating Metal .**
former Disc (2Holes) Moulding
FIG. 1.7. Wirewound (precision) type.
The highest stability with lowest temperature coefficient is still
obtained with wirewound precision resistors (see Fig. 1.7),
although some of the evaporated metal film resistors approach
this but do not yet equal it.
Accuracy {or Tolerance)
Carbon composition resistors are made to approximate target
values and then selected to various values after manufacture.
Selection tolerances are set up and resistors sorted to + 5 per cent,
± 10 per cent and ± 20 per cent of the nominal batch value.
Carbon composition resistors cannot be regarded as accurate to
better than 5 per cent because of the lack of precise control in
their composition and because of a tendency to drift in value.
Pyrolytic or cracked-carbon resistors are accurate to 1 or 2 per
cent, but can be manufactured to about 0-1 per cent if necessary.
Wirewound resistors are accurate to 0-25 per cent and can be
manufactured to 0-05 per cent or even 0-01 per cent if desired.