Electronic symbol

Common circuit diagram symbols (US symbols)

An electronic symbol is a pictogram used to represent various electrical and electronic devices or functions, such as wires, batteries, resistors, and transistors, in a schematic diagram of an electrical or electronic circuit. These symbols are largely standardized internationally today, but may vary from country to country, or engineering discipline, based on traditional conventions.

Standards for symbols

The graphic symbols used for electrical components in circuit diagrams are covered by national and international standards, in particular:

• IEC 60617 (also known as British Standard BS 3939).
• There is also IEC 61131-3 - for ladder-logic symbols.
• JIC JIC (Joint Industrial Council) symbols as approved and adopted by the NMTBA (National Machine Tool Builders Association). They have been extracted from the Appendix of the NMTBA Specification EGPl-1967
• ANSI Y32.2-1975 (also known as IEEE Std 315-1975 or CSA Z99-1975)
• IEEE Std 91/91a: graphic symbols for logic functions (used in digital electronics). It is referenced in ANSI Y32.2/IEEE Std 315.
• Australian Standard AS 1102. (Based on a slightly modified version of IEC 60617, Withdrawn without replacement with a recommendation to use IEC 60617)

The number of standards leads to confusion and errors. Symbols usage is sometimes unique to engineering disciplines and national or local variations to international standards exist. For example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.

Gallery of common electronic symbols

Symbols shown are typical examples, not a complete list.

Traces

• 
  IEC-style trace junction
• 
  Trace crossing

Grounds

• 
  IEC-style ground (GND) symbol
• 
  Signal/Low noise ground (GND) symbol
• 
  IEC-style chassis-ground symbol

Sources

• 
  Battery, single cell and multi-cell
• 
  Battery, multi-cell
• 
  Voltage source
• 
  Controlled voltage source
• 
  Current source
• 
  Controlled current source
• 
  AC voltage source

Resistors

• 
  (a) resistor, (b) rheostat (variable resistor), and (c) potentiometer (All of them are American style symbols)
• 
  (a) resistor, (b) rheostat (variable resistor), and (c) potentiometer (All of them are IEC style symbols)
• 
  Thermistor or Varistor

Capacitors

• 
  IEC-style capacitor, general symbol
• 
  Capacitor, polarized (American)
• 
  Capacitor, variable
• 
  IEC-style ganged (co-moving) variable capacitors
• 
  Trimmer capacitor

Diodes

• 
  Diode
• 
  Zener diode
• 
  Tunnel diode
• 
  Schottky diode
• 
  Light Emitting Diode (LED)
• 
  Photodiode
• 
  Varicap
• 
  Shockley diode
• 
  Silicon-controlled rectifier (SCR)
• 
  Constant-current diode

Inductors

• 
  IEC-style air-cored Inductor
• 
  Inductor with magnetic core (IEEE Std 315)
• 
  IEC-style tapped Inductor

Transformers

• 
  Transformer with center tap
• 
  Transformer with two secondary windings
• 
  Current Transformer
• 
  Zero-Sequence Current Transformer (ZSCT) (also known as a window-type current transformer)
• 
  Bushing-Type Current Transformer
• 
  Voltage Transformer

Transistors

Unipolar

• 
  N-channel junction gate field-effect transistor (JFET)
• 
  P-channel junction gate field-effect transistor (JFET)
• 
  Metal-Oxide-Semiconductor Field-Effect Transistor
• 
  Enhancement mode, N-channel MOSFET
• 
  Enhancement mode, P-channel MOSFET

Bipolar

• 
  NPN bipolar junction transistor (BJT)
• 
  PNP bipolar junction transistor (BJT)
• 
  NPN darlington
• 
  PNP darlington

Vacuum tubes

• 
  Vacuum tube diode
• 
  Vacuum tube triode
• 
  Vacuum tube tetrode
• 
  Vacuum tube pentode

Switches

• 
  Switch, Single Pole/Single Throw (SPST)
• 
  Switch, Single Pole/Double Throw (SPDT)
• 
  Switch, Double Pole/Double Throw (DPDT)
• 
  Pushbutton, Momentary or Spring-Return, make (IEEE Std 315)
• 
  Pushbutton, Momentary or Spring-Return, break (IEEE Std 315)
• 
  Pushbutton, Momentary or Spring-Return, two circuit (IEEE Std 315)

Relays

• 
  American-style relays, SPST, SPDT, DPST, DPDT
• 
  IEC relay symbol, SPDT

Lamps

• 
  Indicating lamp (IEEE Std 315-1975)
• 
  Incandescent lamp
• 
  Incandescent light bulb (as an indicator)
• 
  Neon lamp
• 
  Light bulb

Current limiters

• 
  IEC Fuse (a), equivalent symbols (b,c) (IEEE Std 315-1975)
• 
  Moulded Case Circuit Breaker (MCCB)
• 
  Fuse: IEC (top) and American (lower two)

Electro-acoustic devices

• 
  IEC-style microphone
• 
  Microphone (IEEE Std 315)
• 
  Buzzer
• 
  Loudspeaker (IEEE Std 315)

Antennas

• 
  IEC-style antenna
• 
  IEC-style dipole antenna
• 
  IEC-style loop antenna
• 
  Loop antenna (IEEE Std 315)

Miscellaneous devices

• 
  Phone jacks
• 
  Operational amplifier
• 
  Ferrite bead ring (IEEE Std 315)
• 
  Crystal oscillator
• 
  Hall effect sensor

Gallery of historical electronic symbols

The shape of electronic symbols have changed over time. Some symbols were more prevalent in some countries. The following are historic electronic symbols that might be found in old electronic books and schematics.

Capacitors (historical)

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• 
• 

See also

• Logic gate
• Reference designator
• Symbols for appliance classes

External links

• IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters)
• International standard IEC 60617 DB Graphical symbols for diagrams
• Electrical Schematic Symbols
• Collection of Open Source Electrical, Pneumatic, Hydraulic and Electronic Symbols
• Circuit Symbols of Electronic Components
• Electrical & Electronic Drawing Symbols
• Collection of Electrical and Electronic Symbols
• Circuit Schematic Symbols
• Collection of Electrical and Electronic Schematic Symbols