The following are the details about circuit symbols:
1. Definition and function of circuit symbols
Circuit symbols are graphic symbols used to represent various electronic components, devices and connections in circuit diagrams. They provide a concise and standardized way to depict the structure and function of circuits, allowing engineers, technicians and students to easily understand the design and working principles of circuits. For example, by using simple symbols to represent components such as resistors, capacitors, inductors, etc., people can quickly draw complex circuit schematics without drawing the physical shapes of the actual components.
2. Common circuit symbols
Power supply symbol
Battery symbol: represented by two parallel vertical lines, one long and one short. The long vertical line represents the positive pole of the battery and the short vertical line represents the negative pole. For example, in a simple flashlight circuit, the battery is represented by this symbol, which provides power to the circuit.
DC power supply symbol: usually a circle with a "+" and "-" sign inside, indicating a power supply that outputs direct current. This power supply is widely used in electronic devices such as mobile phone chargers.
AC power supply symbol: also a circle with a "~" symbol inside, indicating a power supply that outputs alternating current. For example, the AC power supply connected to a household socket has a periodic change in voltage and current direction.
Symbols for passive components
Resistor symbol: It is represented by a rectangle with lead wires at both ends. The unit of resistance is ohm (Ω), and its function is to limit the flow of current. For example, in a simple voltage divider circuit, the voltage is distributed by adjusting the resistance value of the resistor.
Capacitor symbol: There are two common representation methods. One is represented by two parallel straight lines, representing a flat plate capacitor; the other is a circular symbol with two parallel plates. The unit of capacitance is farad (F), which can store charge and plays an important role in filtering circuits and coupling circuits.
Inductor symbol: It is usually represented by a series of curved lines, similar to a spiral. The unit of inductance is Henry (H), which is mainly used to store magnetic field energy and is often used in filtering and oscillation circuits.
Active component symbol
Diode symbol: It consists of a triangle and a vertical line, with the vertex of the triangle pointing in the direction of the current. The diode has unidirectional conductivity and only allows current to flow from the anode (the vertex side of the triangle) to the cathode (the side of the vertical line). For example, in a rectifier circuit, a diode is used to convert alternating current into direct current.
Transistor symbol: There are two types: NPN and PNP. The NPN transistor symbol is a circle with two slashes inside that divide it into three areas, representing the emitter (E), base (B) and collector (C), and the emitter arrow points outward; the PNP transistor symbol is similar, but the emitter arrow points inward. Transistors are mainly used to amplify signals and as electronic switches.
Connection and other symbols
Wire symbol: Represented by a straight line, used to connect various circuit components to indicate the path of current. In a circuit diagram, when the wires cross, if there is no connection point, they are usually simply crossed; if there is a connection point, it will be represented by a solid black dot.
Ground symbol: Usually represented by three short downward slashes or a triangle, it represents the zero potential reference point in the circuit and is the common reference benchmark for all signals.
3. Standards for circuit symbols
There are many standards for circuit symbols internationally, such as the Institute of Electrical and Electronics Engineers (IEEE) standards and the International Electrotechnical Commission (IEC) standards. These standards ensure the consistency and universality of circuit symbols around the world, allowing engineers from different countries and regions to accurately understand and communicate circuit designs. For example, in a circuit diagram that complies with the standards, anyone familiar with these standards can correctly identify the various components and their connections, thereby analyzing, testing, and manufacturing the circuit.