Electronic Circuit Symbols & Notations
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ELECTRONIC CIRCUIT SYMBOLS & NOTATIONS by Ray Marston — been editor or technical editor of major industrial countries have Now magazine, and Figure 2 four different electronics maga- their own individual preferred styles shows the same diagram drawn in zines, have written about 2,000 for electronic circuit symbols and the house style of the German Ray Marston technical articles, and have written notations, but these styles are not electronics magazine Elrad, which 31 electronics engineering books. too rigidly applied and often vary uses a simple rectangular symbol looks at some Many of my magazine articles are considerably between one techni- (rather than a zig-zag) to represent published internationally, and — in cal publisher and another, accord- a resistor. controversial various periods — have appeared ing to the ‘house style’ of the indi- Regarding the German capaci- aspects of regularly in magazines in the UK, vidual publishing company. In the tor symbols, the two parallel lines Germany, Holland, Australia, USA, for example, the so-called used to represent C1 and C3 indi- modern circuit Canada and the USA. ‘US Customary’ system is normally cate that these are ordinary non- Of my 31 books, two were first used, but the precise details of the electrolytic components, and the symbology in published in Germany, and the rest system vary significantly between black and white rectangles used to in the UK; several were later pub- different electronics magazines. represent C2 and C4 indicate that this special lished in the USA. Between them, Figures 1 to 5 show examples these are electrolytic capacitors; feature article. these books have been translated of how exactly the same circuit dia- the ‘+’ signs associated with C2 and Ω into about a dozen different lan- gram can vary when published by C4 indicate that the capacitors are guages (often with suitably modi- particular electronics magazines in polarized types, and that the white fied circuit dia- grams), including INTRODUCTION Russian, Hindus- tani, and most Back in May ’97, I started writ- major European ing regular ‘circuit application’ fea- tongues. ture articles for Nuts & Volts maga- Throughout zine. All of these articles are specif- the past five years, ically aimed at experienced design I have produced engineers and competent electron- most of the art- ics enthusiasts (rather than at work and circuit novices or complete beginners), diagrams that ac- and are unusual in two special company my respects. books and maga- Figure 1. Circuit in the house style of Figure 2. Circuit in the house style of They are unusual, first, zine articles Electronics Now magazine (USA). Elrad magazine (Germany). because most of them carry (on (including those average) about 20 illustrations or used in Nuts & practical circuit diagrams, and sec- Volts), using a ond, because all of the circuit dia- Corel DRAW 3 art- grams use International style — work/CAD pack- rather than US Customary — circuit age and my private symbols and component notations. symbols library. I All of these articles have been generate an aver- well received by most Nuts & Volts age of about 350 fans, but some readers (who admit diagrams a year, to being electronics novices) have and have thus pro- complained that they are quite duced about 1,750 bemused by the component nota- technical illustra- tions that I use in these articles. I tions and diagrams suspect that quite a few other Nuts in the past five Figure 3. Circuit in the house style of Electronics Today International Figure 4. Circuit in the house style of & Volts fans may feel the same way years. Electronics World magazine (UK). so, in this special article, I aim to As a conse- magazine (UK). explain the operation of the quence of all the International style electronic circuit above, I have lots of professional particular parts of the diagram system, and to explain the experience in the technical publish- western world. The circuit system’s advantages over the US ing business and in generating is that of a simple LM386 Customary system. This is a fairly modern circuit diagrams, and am audio power amplifier, controversial subject and may familiar with many of the different with its voltage gain set at annoy some readers, so I will start electronic circuit symbol and nota- x200 by C4 and with its off by presenting my qualifications tion systems that are used in vari- output protected by the for writing about it, as follows: ous parts of the world and with their C3-R1 Zobel network and specific advantages and disadvan- loaded by an eight-ohm MY QUALIFICATIONS tages compared to other systems. speaker. Figure 1 shows the I have been an electronics TYPICAL CIRCUIT diagram drawn using the design engineer and writer/author familiar US Customary DIAGRAMS Figure 5. Circuit drawn in typical for over 30 years. During that peri- system, using the basic International style. od, I have — amongst other things In the western world, most house style of Electronics Reprinted from December 1998 Nuts & Volts Magazine. All rights reserved. No duplication permitted without permission from T & L Publications, Inc. 1 ELECTRONIC CIRCUIT SYMBOLS & NOTATIONS terminal is positive. simplified European style, and com- For most American readers, the was first specified, it was required In the UK, British electronics ponent values are given in formal only problems presented by the to be designed as a simple easily- magazine sales are dominated by ‘International’ style, which is non-US Figure 2 to 5 diagrams printed code that indicates an elec- six popular titles. Half of these use explained in a later major section of relate to the International compo- tronic component’s value clearly, the zig-zag resistor symbol in their this article. nent value notation systems that briefly, without ambiguity, and with a circuit diagrams, and half use the Note in Figures 1 to 5 that all they use, which all notate the 10 minimum loss of clarity if poorly simple rectangular symbol. Figure 3 five basic diagrams are quite easy resistor as 10R, and notate printed. shows the Figure 1 diagram to understand, in spite of the varia- 0.047µF capacitor C3 as 47n (the This last requirement immedi- redrawn in the house style of one of tions in the styles of the symbols odd 220u — rather than 220µ — ately ruled out the use of decimal the most popular British electronics used to represent resistors, capaci- notation used on C4 in Figure 3 is points in the new code system, and magazines, Electronics Today tors, ground points, and loudspeak- simply a house style peculiarity the requirement for brevity called International, which uses the simple ers. Also note that the variable used by one UK magazine). Before for (1) the elimination of all super- rectangle to represent a resistor, resistor is notated by RV (Resistor, explaining how the International fluous information from the code, and uses two black rectangles to Variable) in the four non-US dia- notation system works, I will explain and (2) for sensible compression of represent an ordinary non-elec- grams, but by a simple R in Figure why it was developed. the remaining data. trolytic capacitor. 1. Finally, note that the Figure 2 to 5 Regarding point (1) in the The most prestigious British diagrams use a plain R instead of EVOLUTION OF THE ‘brevity’ requirement, note that in electronics magazine is Electronics the symbol to indicate a resistor’s ‘INTERNATIONAL’ circuit diagrams, when indicating World, which is aimed directly at value in ohms, and (in Figures 2 the value of a symbolic resistor, professional engineers and man- and 4) use the symbol only to indi- SYSTEM capacitor, or inductor, it is self-evi- agers; it has its own basic house cate the loudspeaker’s nominal Prior to the mid 1970s, the dent that the component’s value is style for circuit diagrams, but varies impedance value. electronic component notation sys- expressed in basic units of ohms, the style slightly from article to arti- The easily-understood Figure 1 tems used by most European coun- Farads, or Henrys, and the new cle. Figure 4 shows Figure 1 to 5 circuits are analog designs. tries were similar to the present US code’s design specification thus redrawn in this magazine’s basic Foreign digital designs can be far Customary system and were loose- demanded the elimination of this house style; note the awkward mix- harder to understand. Figure 6, for ly based on the metric scientific superfluous ‘postscript’ data from ture of upper-case and subscript example, shows some of the crazy notation system that — in 1960 — the printed code when used in cir- characters used to denote compo- official symbols used to represent became officially known as SI cuit diagrams (but not necessarily in nent numbers, etc. simple logic gates in Europe. In (Système Internationale d’Unités). normal printed text). Finally, Figure 5 shows Figure 1 practice, most European electron- In the 1960s, however, major Regarding point (2) in the drawn in my own particular version ics book and magazine publishers developments in the semiconductor ‘brevity’ requirement, this was to be of the International circuit diagram sensibly adhere to the American industry resulted in a great increase aided by using a fixed three- style (which I use in my Nuts & Volts MIL/ANSI symbol system, which is in the complexity of practical circuit decade spacing between the deci- articles), in which resistors are also used in the normal designs, and industry and com- mal ‘multiplier’ units used to indi- drawn as zig-zags, capacitors are in ‘International’ diagram system. merce began looking for ways of cate a component’s value. producing the result- Figure 7 lists the range of dec- ingly complex circuit imal multiplier units — using basic diagrams and literature SI scientific notation and three- with greater efficiency.