Electronic Component Circuit Symbols

- overview of the electronic circuit symbols or schematic symbols, standards used in circuit diagrams and further pages with sections of circuit symbols.

Circuit symbols are used for electronic circuit diagrams or circuit schematics. The various schematic symbols are used to represent different electronic components and devices in circuit diagrams from wires to batteries and passive components to semiconductors, logic circuits and highly complicated integrated circuits.

By using a common set of circuit symbols in schematics, it is possible for electronic engineers around the globe to communicate circuit information concisely and without ambiguity.

Although there are a number of different standards in use for the different circuit symbols around the globe, the differences are normally small, and because most systems are well known, there is normally little room for ambiguity.

Circuit symbol systems

There is a number of different systems used for schematic symbols around the globe. The main ones are listed below:

  • IEC 60617:   This standard is issued by the International Electrotechnical Commission, and this standard for electronic component symbols is based on the older British Standard, BS 3939 which in turn was developed from the much older British Standard 530. Often reference is made to BS electric component standard, and the IEC standard is now the one that is used. The database includes around 1750 circuit symbols overall.
  • ANSI standard Y32:   This standard for electronic component symbols is the American one and is also known as IEEE Std 315. This IEEE standard for circuit symbols has various release dates.
  • Australian Standard AS 1102:   This is an Australian standard for electronic component symbols.

Of these the IEC and ANSI/IEEE standards for electronic symbols, i.e. schemtic symbols are those that are most widely used. Both are quite similar to each other although there are a number of differences. However as many circuit diagrams are used globally, both systems will be well known to most electronics engineers.

Circuit notation and reference designators

When developing a circuit diagram or schematic, it is necessary to identify the individual components. This is particularly important when using a parts list as the components on the circuit diagram can be cross related to the parts list or Bill of Materials. It is also essential to identify components as they are often marked on the printed circuit board and in this way the circuit and the physical component can be identified for activities such as repair, etc..

In order to identify components, what is termed a circuit reference designator is used. This circuit reference designator normally consists of one or two letters followed by a number. The letters indicate the type of component, and the number, defines which particular component of that type it is. An example may be R13, or C45, etc..

In order to standardise the way in which components are identified within schematics, the IEEE introduced a standard IEEE 200-1975 as the "Standard Reference Designations for Electrical and Electronics Parts and Equipments." This was later withdrawn and later the ASME (American Society of Mechanical Engineers), initiated the new standard ASME Y14.44-2008.

Some of the more commonly used circuit reference designators are given below:

More commonly used Circuit Schematic Reference Designators
Reference Designator Component Type
ATT Attenuator
BR Bridge rectifier
BT battery
C Capacitor
D Diode
F Fuse
IC Integrated circuit - an alternative widely used non-standard abbreviation
J Connector jack (normally but not always refers to female contact)
L Inductor
LS Loudspeaker
P Plug
PS Power supply
Q Transistor
R Resistor
S Switch
SW Switch - an alternative widely used non-standard abbreviation
T Transformer
TP Test point
TR Transistor - an alternative widely used non-standard abbreviation
U Integrated circuit
VR Variable resistor
X Transducer
XTAL Crystal - an alternative widely used non-standard abbreviation
Z Zener diode
ZD Zener diode - an alternative widely used non-standard abbreviation

Circuit diagram symbols

There are very many circuit diagram symbols for different components. Accordingly the different symbols have been grouped into different sections which have been provided on the pages as set out below:

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