Electronic Circuit Symbols

One device may be connected to another through wires. This is represented by drawing “blobs” on the point where they are shorted.

When circuits are drawn some wires may not touch others. This can only be shown by bridging them or by drawing them without blobs. But bridging is commonly practised as there will not arise any confusion.

A battery has more than a cell and is used for the same purpose. The smaller terminal is negative and the larger one is positive. Abbreviated as ‘B’.

Used as an ac power supply. Consists of two coils, the primary and secondary that are linked together through an iron core. There is no physical connection between the two coils. The principle of mutual inductance is used to obtain power. Abbreviated as ‘T’.

Used in electronic circuits to represent the 0 volts of the power supply. It can also be defined as the real earth , when it is applied in radio circuits and power circuits.

A resistor is used to restrict the amount of current flow through a device. Abbreviated as ‘R’.

A rheostat is used to control the current flow with two contacts. Applicable in controlling lamp brightness, capacitor charge rate, etc.

A potentiometer is used to control the voltage flow and has three contacts. Have applications in changing a mechanical angle change to an electrical parameter. Abbreviated as ‘POT’.

Presets are low cost variable resistors that are used to control the charge flow with the help of a screw driver. Applications where the resistance is determined only at the end of the circuit design.

Capacitor is a device that is used to store electrical energy. It consists of two metals plates that are separated by a dielectric. It is applicable as a filter, that is, to block DC signals and allow AC signals. Abbreviated with the letter ‘C’.

Used to vary the capacitance by turning the knob. A type of variable capacitor is the trimmer capacitor that is small in size. The notations are all the same.

A diode is used to allow electric current to flow in only one direction. Abbreviated as ‘D’.

LED is used to emit light when a current is passed through the device. It is abbreviated as LED.

After a breakdown voltage, the device allows current to flow in the reverse direction as well. It is abbreviated as ‘Z’.

Photodiode works as a photo-detector and converts light into its corresponding voltage or current.

Tunnel Diode is known for its high-speed operation due to its application in quantum mechanical effects.

The Schottky Diode is known for its large forward voltage drop and hence has great applications in switching circuits.

This is a transistor with a layer of P-doped semiconductor fixed between two layers of N-doped semiconductors that act as the emitter and collector. Abbreviated as ‘Q’.

This is a transistor with a layer of N-doped semiconductor fixed between two layers of P-doped semiconductors that act as the emitter and collector. Abbreviated as ‘Q’.

The working of a phototransistoris similar to that of a bipolar transistor with a difference that it converts light into its corresponding current. The phototransistor can also act as a photodiode if the emitter is not connected.

Like a transistor, a FET has three terminals, the Gate, Source and Drain. The device has an electric field that controls the conductivity of a channel of one type charge carrier in a semiconductor substance.

The Junction Field Effect Transistor (JFET) is the simplest type of FET with applications in Switching and voltage variable resistor. In an N-channel JFET an N-type silicon bar has two smaller pieces of P-type silicon material diffused on each sides of its middle part, forming P-N junctions.

P-channel JFET is similar in construction to N-channel JFET except that P-type semiconductor base is sandwiched between two N-type junctions. In this case majority carriers are holes.

Abbreviated as MOSFET. MOSFET is a three terminal device and is controlled by a gate bias. It is known for its low capacitance and low input impedance.

The enhancement MOSFET structure has no channel formed during its construction. Voltage is applied to the gate, so as to develop a channel of charge carriers so that a current results when a voltage is applied across the drain-source terminals. Abbreviated as e-MOSFET.

In the depletion-mode construction a channel is physically constructed and a current between drain and source is due to voltage applied across the drain-source terminals. Abbreviated as d-MOSFET.

If all the inputs of an AND gate are HIGH, then the output will also be HIGH. If any one of them is LOW, the output will also be LOW.

Short form for NOT AND Gate. Of all the inputs are HIGH, the output will be LOW. If any one input is LOW, the output will be HIGH.

If any one of the input is HIGH, the output will also be HIGH. If both inputs are LOW, the output will also be LOW.

Short form for NOT OR. If both inputs are LOW, the output will also be LOW. For other cases, the output will be HIGH.

Short form for Exclusive NOR. If both inputs are either in LOW state r HIGH state, the output will be LOW. If both inputs are different, the output will be HIGH.

Short form for Exclusive NOT OR. If both the inputs are the same, the output will be HIGH. If both are different, the output will also be different.

Also known as the inverter Gate. There is only one input for this gate. If the input is HIGH, the output will be LOW. If the input is LOW, the output will be HIGH.

An Ammeter is used to measure the current that passes through the circuit at a particular point.

A galvanometer is used to measure very small currents in the order of 1 milli ampere or less.

An oscilloscope is used to measure the voltage and time period of signals along with their shape display.

It is abbreviated as LDR. Light Dependent Resistor is used to convert light into its corresponding resistance. Instead of directly measuring the light, it senses the heat content and converts it onto resistance.

Instead of directly measuring the light, a thermistor senses the heat content and converts it into resistance. Abbreviated as ‘TH’.

The push to break switch is usually kept in the ON state (closed). It turns to OFF state (open) only when the switch is pressed.

Also known as the ON/OFF switch. This switch allows the flow of current only when it is kept ON. Abbreviated as SPST.

Also known as the 2-way switch. It can be also called as an ON/OFF/ON switch as it has an OFF position in the center. The switch causes the flow of current in two directions, depending on its position. It can be abbreviated as SPDT.

Abbreviated as DPST. Can also be called as a dual ON-OFF switch. This is used to isolate between the live and neutral connections in the main electrical line.

Abbreviated as DPDT. The switch uses a central OFF position and is applied as reversing switch for motors.

Relay is abbreviated as ‘RY’. This device can easily switch a 230 Volt AC mains circuit. It has three switching stages called Normally Open (NO). Normally Closed (NC), and Common (COM).

This device is used for converting sound to its corresponding electrical energy. Abbreviated as ‘MIC’.

Does the same operation as an earphone, but converts an amplified version of the electrical energy into its corresponding sound.

Used to amplify a signal. It is mainly used to represent a whole circuit rather than just one component.

Inductor is used to produce a magnetic field when a certain current is passed through a coil of wire. The wire is coiled on a soft iron core. Have applications in motors, and tank circuits. Abbreviated as ‘L’.

This device is used to convert electrical energy into mechanical energy. Can be used as a generator as well. Abbreviated as ‘M’.

Used to produce a sound as the output, according to the electrical energy produced as the input.

It is used to produce an output sound corresponding to the electrical energy in the input.