Electrical Symbols & Electronic Symbols

Electrical symbols or electronic circuits are virtually represented by circuit diagrams. There are some standard symbols to represent the components in a circuits. This article gives some of the frequently used symbols for drawing the circuits. There are many electrical and electronic schematic symbols are used to signify basic electronic or electrical device. These are mostly we used for draw circuit diagrams.

Below are different kind of symbols we mentioned category wise. Hope this information will helps to understand clearly.

Electrical Symbols & Electronic Symbols

	SYMBOL	COMPONENT	MEANING
		WIRES
		Wires	Represents a conductor that conducts electrical current. Also called a power line or electric line or wire.
		Connected Wires	Represents the connection of two conductors. Dot shows the junction point.
		Unconnected Wires	Represents two unconnected wires/conductors. Any of the two methods can be followed. Drawing two lines perpendicularly is an older method of representing unconnected wires.
		Input Bus Line	Represents a bus for input or incoming data.
		Output Bus Line	Represents a bus for output or outgoing data.
		Terminal	Represents start or end point.
		Bus Line	Represents a number of conductors joined together to form a bus wire.
		SWITCHES
		Push Button (Normally Open)	This switch is in ON state when the button is pressed otherwise it is in OFF state.
		Push Button (Normally Closed)	This switch is initially in ON state. This goes to OFF state when it is released.
		Spst Switch	Single pole single throw is abbreviated as SPST. This allows the flow of current when the switch is closed. This acts as ON/OFF switch. Poles define the number of circuits it can be connected to and throws defines the number of positions that a pole connects.
		Spdt Switch	Single pole double throw is abbreviated as SPDT. This switch allows the current to flow in any one of the two directions by adjusting its position.
		Dpst Switch	Double pole single throw is abbreviated as DPST. This switch can drive two circuits at a time.
		Dpdt Switch	Double pole double throw is the full form of DPDT. This can be defined as two independent SPDT switches. This can connect the four circuits by changing the position.
		3 Position Rotary or Multi Switch	This switch is operated by rotation. This has 3 positions. Often used in fan control, citizen band radio and tuning.
		5 Position Rotary or Multi Switch	This switch is operated by rotation. This has 5 positions.
		Relay Switch	This represents the relay switch. This can control the AC Loads using the DC voltage applied to the coil.
		SOURCES
		AC Supply	This represents AC supply in the circuit.
		DC Supply	This represents the DC power supply. It applies DC supply to the circuit.
		Constant Current Source	Current source is used to deliver or absorb electric current. The symbol represents an independent current source which delivers constant current.
		Controlled current Source	It is a dependent current source. Usually depends on other sources (voltage or current).
		Controlled Voltage Source	It is a dependent voltage source. Usually depends on other sources (voltage or current).
		Single Cell Battery	This provides supply to the circuit.
		Multi Cell Battery	Combination of multiple single cell batteries or a single large cell battery. The voltage is usually higher.
		Wave Generators
		Sinusoidal Generator	Represents sine wave generator.
		Pulse Generator	Represents pulse or square wave generator.
		Triangular Wave	Represents triangular wave generator.
		GROUND SYMBOLS
		Ground	It is equivalent to theoretical 0V and is used as zero potential reference. It is the potential of perfectly conducting earth.
		Signal Ground	It is a reference point from which the signal is measured. There may be several signal grounds in a circuit due to the voltage drops in a circuit.
		Chassis Ground	Connected to the chassis of the circuit. It is the frame or box in which the circuit is built. It acts as a barrier between user and the circuit and prevents electric shock.
		RESISTOR SYMBOLS
		Fixed Resistor	It is a device that opposes the flow of current in a circuit. These two symbols are used to represent fixed resistor.
		VARIABLE RESISTOR
		Potentiometer	It is a three terminal variable resistor which acts as an adjustable voltage divider. It is used in power supplies that produce varying DC voltages like volume controls or joysticks.
		Rheostat	It is a two terminal variable resistor. They are generally used to control the current in the circuit. Generally used in tuning circuits and power control applications like heaters, ovens etc
		Preset	It is a mini variable resistor. It is also called Trimmer Resistor or Trim Pot. The resistance is adjusted with rotary control present on top of it with the help of a screw driver. They are used to adjust the sensitivity of the circuit like temperature or light.
		Thermistor	It is a temperature sensitive resistor. They are used in temperature sensing, current limiting circuits, over-current protection circuits etc.
		Varistor	It is a Voltage Dependent Resistor. It has non-linear current-voltage characteristics. Generally used in circuit protection from voltage surges and excessive transient voltages.
		Magneto Resistor	They are also called as Magnetic Dependent Resistors (MDR). The resistance of magneto resistor varies according to the external magnetic field strength. They are used in electronic compass, ferrous material detection, position sensors etc.
		LDR	They are also called as Photo Resistors. The resistance of LDR varies with the intensity of the light incident on it. They are generally used in light sensing applications.
		Tapped resistor	A wire-wound type fixed resistor with one or more terminals along its length. Generally used in voltage divider applications.
		Attenuator	It is a device used to lower the power of a signal. They are made from simple voltage dividers and hence can be classified in the family of the resistors.
		Memristor	Memristor is a device derived from the word memory resistor. The resistance of memristor is varied according to the direction of flow of charge. Memristors can be used in signal processing, logic/computation, non-volatile memory etc.
		CAPACITOR SYMBOLS
		Non Polarized Capacitor	Capacitor stores the charge in the form of electrical energy. These two symbols are used for non-polarized capacitor. Non-polarized capacitors are big in size with small capacitance. They can be used in both AC and DC circuits.
		Polarized Capacitor	Polarized capacitors are small in size but have high capacitance. They are used in DC circuits. They can be used as filters, for bypassing or passing low frequency signals.
		Electrolytic Capacitor	Almost all electrolytic capacitors are polarized and hence used in DC circuits
		Feed through Capacitor	They provide low impedance path to ground for high frequency signals
		Variable Capacitor	The capacitance of the variable capacitor can be adjusted by turning the knob. They are widely used to adjust the frequency , that is for tuning.
		INDUCTORS
		Inductor	Inductor stores the charge in the form of magnetic field. This contains a conductor wound in the form of a coil. The current flowing in the coil induces voltage by phenomena of faradays law of electromagnetic induction. Here the coil is wound on non-magnetic forms like plastic or ceramic.
		Iron Core Inductor	These are used as substitutes to ferrite core inductors. Ferrite core or Ferromagnetic inductors have high permeability and require air gap to reduce it. Iron powdered core inductors have this air gap integrated.
		Ferrite Core Inductors	Core material, in this type of inductors is made of ferrite material. These are mostly used to suppress the interference of electromagnetic waves.
		Center Tapped Inductors	These are used in coupling of signals,
		Variable Inductors	Movable ferrite magnetic core variable inductors are most common. The inductance is varied by sliding the core in or out of the coil.
		DIODES
		Pn Junction Diode	A PN junction diode allows the current to flow only in forward bias condition. These diodes can be used in clipping and clamping circuits , as rectifiers in dc circuits etc.
		Zener Diode	In forward bias condition, it acts as normal diode and allows current. It also allows current to flow in reverse bias condition when the voltage reaches a certain break-down point. Generally used in voltage regulator and over voltage protection circuits.
		Photodiode	Photodiode detects the light energy and converts it into current or voltage by a mechanism called photoelectric effect. These are used in CD players , Cameras etc.
		Led	Light emitting diode is similar to PN junction diode but they emit energy in the form of light instead of heat. These are mostly used in indication , lightening applications.
		Varactor Diode	Varactor diode is called varicap or variable capacitance diode. The capacitance of this diode varies according to the applied input voltage. This is used in frequency controlled oscillators , frequency multipliers etc.
		Schottky Diode	The symbol represents Schottky diode. It has low forward voltage drop and it can switch rapidly. Used in voltage clamping, rectifiers, reverse current and discharge protection
		Shockley Diode	This is a four layer diode. This had fast switching operation and hence is used in switching applications.
		Tunnel Diode	This is also known as Esaki diode.It can switch very fastly and can perform well in micro wave frequency range. This is used in oscillator circuits and micro wave circuits.
		Thyristor	It consists of four layers of alternating P and N materials. They act as bistable switches and are used in circuits where high voltages and currents are involved.
		Constant Current Diode	Also called as Current Limiting Diode or Current Regulating Diode. It limits the current to a specified maximum value.
		Laser Diode	The laser diode is similar to light emitting diode. The active region is formed in intrinsic region in PIN structure. Laser diodes find its applications in laser printing, laser scanning etc.
		TRANSISTOR SYMBOLS
		NPN	It is made of combination of P-type semiconductor between two N-type semiconductors. It is switched ON when the base-emitter junction is forward biased. They are commonly used for amplifying and switching applications.
		PNP	It is made of combination of N-type semiconductor between two P-type semiconductors. It is switched ON when the base-emitter junction is reverse biased. These are used for amplifying and switching applications.
		JFET	Junction field effect transistor is a unipolar device and is voltage controlled device. The gate junction is reverse biased for its operation.It is used as buffer amplifier, analog switch, oscillators etc.
		N- Channel JFET	N-channel JFET is made by n-type silicon bars which form two PN junctions at the side. Majority charge carriers here are electrons.
		P-Channel JFET	P-Channel JFET is made by p-type silicon bar which forms two PN junctions at the side. Majority charge carriers here are holes.
		MOSFET	MOSFET is similar to JFET but it is operated in enhancement mode also that is, it increases the width of depletion layer. This can be operated in both enhancement and depletion mode. They are used in SMPS, amplifiers , oscillators etc.
		Enhancement MOSFET	The enhancement mode MOSFET has positive gate operation. It induces negative charges into the n-channel and thus number of negative charges increases, enhancing the channel conductivity.
		Depletion MOSFET	The depletion mode has negative gate operation. This decreases the width of the depletion layer.
		Phototransistor	The photo transistor converts the light energy falling on it to its corresponding electrical energy. This can be used in light sensing applications.Base is left disconnected as light is used to enable the flow of current.
		Photo Darlington	Photo Darlington Transistor is similar to phototransistor with very high gain and sensitivity
		Darlington Transistor	This is a configuration of pair of transistors, which produces high current gain. They are used in power regulators, output stages of audio amplifiers, display drivers etc.
		LOGIC GATES
		And Gate	This is the basic gate and it implements logical conjunction. The output of the AND gate is high, only if both the inputs are high otherwise both are low.
		Or Gate	The OR gate implements logical disjunction.The output is high if any one of the inputs is high.
		Nand Gate	It is complement of AND gate. The output is low only when both the inputs are high, otherwise it is high. Any Boolean function can be implemented using combination of NAND gates
		Nor Gate	NOR gate is a not OR gate. Output of this gate is high, if both the inputs are Low, otherwise it is High.
		Not Gate	Inverter or NOT gate implements logical negation. This gate inverts the input.
		Exor	This gate implements exclusive OR logic. The output of this gate is high ,if both the inputs are different.
		Exnor	This gate implements negation of EXOR logic. The output of this gate is high , only if the two inputs are identical.
		Buffer	It is an audio signaling device. Generally used in alarms, timers and for confirmation messages.
		Tri-State Buffer	Similar to a normal buffer but with a control signal. In case of active high buffer, it operates normally only when control signal is 1. In case of active low buffer, it operates normally only when control signal is 0.
		Flip Flop	Flip flop is the also a memory element but this is a synchronous device. The figure below shows the basic D-flip-flop.
		AMPLIFIERS
		Basic Amplifier	An amplifier is a device that amplifies a relatively small input signal i.e. it increases the power of the signal. They are used in communication systems, audio devices etc
		Operational Amplifier	Operational Amplifier (Op Amp) is a voltage amplifier with very high gain. The input is differential. They are used in instrumentation devices, signal processing, control systems etc
		ANTENNA
		Antenna	This symbol belongs to Aerial or Antenna. It converts electrical power into radio waves. It is used in wireless communication to transmit or receive the signals.
		Loop Antenna	Loop antenna is named after its loop like shape of wire or other electrical conductor. They are used as receiving antennas in low frequency range.
		Dipole Antenna	It is most widely used antenna. They consist of two bilaterally symmetrical conductive elements. Generally used in set-top TV, shortwave transmission and FM receivers.
		TRANSFORMER
		Transformer	Transformer is the basic element that transfers energy in one circuit to the other circuit through electromagnetic induction. They are generally used in electric power applications to increase or decrease the voltage of AC current.
		Iron Core	Uses a piece of magnetic material as core. Generally Ferro magnetic metals like iron are used. The core has high permeability and is used to confine the magnetic field.
		Center Tapped	The center tapped transformer is similar to a normal transformer except that it has its secondary winding divided into two parts with same number of turns in each part. This results in two individual output voltages across two line ends. Used in rectifier circuits.
		Step Up Transformer	The no. of turns in secondary winding is more than that of primary winding. The output voltage is higher than input voltage. Significantly used in inverters.
		Step Down Transformer	The no. of turns in secondary winding is less than that of primary winding. The output voltage is lesser than input voltage. It is widely used in low power applications.
		MISCELLANEOUS
		Buzzer	This is sound producing device. This produces buzz sound when the voltage is applied.
		Loud Speaker	This is also an audio device. The electrical signal is converted into sound signal here.
		Light Bulb	The symbol represents the light bulb. The bulb glows when required voltage is applied.
		Motor	This converts the electric energy to mechanical energy.
		Fuse	Symbol represents the fuse that protects the circuit from over current.
		Microphone	It converts sound signals to electrical signals.
		Crystal Oscillator	Used to generate clock signal of very precise frequency.
		ADC	Analog to Digital converter is used convert analog signals (usually voltage) to digital values.
		DAC	Digital to Analog converter is used to convert digital code to analog signals.
		Thermocouple	It is used to measure temperature.