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How to Identify Circuit Symbols

Electronic symbol

Common circuit diagram symbols (US symbols)

An electronic symbol is a pictogram used to represent various electrical and electronic devices (such as wires, batteries, resistors, and transistors) in a schematic diagram of an electrical or electronic circuit. These symbols can (because of remaining traditions) vary from country to country, but are today to a large extent internationally standardized. Some symbols represent components (such as vacuum tubes) which ceased to be used routinely as newer technologies were introduced.

Contents

  • 1Standards for symbols
  • 2Gallery of common electronic symbols
    • 2.1Traces
    • 2.2Circuit Return
    • 2.3Sources
    • 2.4Resistors
    • 2.5Capacitors
    • 2.6Inductors
    • 2.7Transistors
      • 2.7.1Unipolar
      • 2.7.2Bipolar
    • 2.8Diodes
    • 2.9Antennas
    • 2.10Vacuum tubes
    • 2.11Switches
    • 2.12Relays
    • 2.13Lamps
    • 2.14Current Limiters
    • 2.15Transformers
    • 2.16Acoustic Devices
    • 2.17Miscellaneous
  • 3Gallery of historical electronic symbols
    • 3.1Capacitors (historical)
  • 4References

1 Standards for symbols

There are several national and international standards for graphical symbols in circuit diagrams, in particular:

  • IEC 60617 (also known as British Standard BS 3939).
  • 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.

Different symbols may be used depending on the discipline using the drawing. For example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics. National and local variations to international standards also exist.

2 Gallery of common electronic symbols

Symbols shown are typical examples, not a complete list.

2.1 Traces

 

  •    
     IEC-style trace junction  Trace crossing

2.2 Circuit Return

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

Sources

  • Single cell, multi-cell battery
  • Battery, multi-cell
  • Voltage source
  • Controlled voltage source
  • Current source
  • Controlled current source
  • AC voltage source

Resistors[edit]

  • (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

Capacitors[edit]

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

Inductors[edit]

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

Transistors[edit]

Unipolar[edit]

  • 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[edit]

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

Diodes[edit]

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

Antennas[edit]

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

Vacuum tubes[edit]

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

Switches[edit]

  • Switch, Single Pole/Single Throw (SPST)
  • Switch, Single Pole/Double Throw (SPDT)
  • Switch, Double Pole/Double Throw (DPDT)
  • Momentary switch, make (IEEE Std 315)
  • Momentary switch, break (IEEE Std 315)
  • Momentary switch, two circuit (IEEE Std 315)

Relays[edit]

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

Lamps[edit]

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

Current Limiters[edit]

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

Transformers[edit]

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

Acoustic Devices[edit]

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

Miscellaneous[edit]

  • Phone jacks
  • Operational amplifier
  • Ferrite bead ring (IEEE Std 315)

Gallery of historical electronic symbols[edit]

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)[edit]

  • Capacitor old.svg
  • Capacitor old with polarity.svg
  • Polarized capacitor symbol 3.svg

 

References 

  1.   Circuit Symbols for all Electronic Components. Talking Electronics, 2013. Retrieved 01 Apr 2015.
  2.   Electrical Symbols & Electronic Symbols. RapidTables, 2012. Retrieved 17 April 2016.
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