1. Simple definition of passive devices
If an electronic component works without any form of power supply inside, it is called a passive device.
From the circuit nature, passive devices have two basic characteristics:
(1) It either consumes electric energy or converts it into other energy in different forms.
(2) It can work normally only by inputting signals and without external power supply.
2. Basic definition of active devices
If an electronic component has an internal power supply when working, it is called an active device.
As far as circuit characteristics are concerned, active devices have two basic characteristics:
(1) itself consumes electricity.
(2) In addition to the input signal, there must be an external power supply to work normally.
It can be seen that active devices and passive devices have completely different requirements for the working conditions and working modes of circuits, which must be paid great attention to in the learning process of electronic technology.
First, common passive electronic equipment
Passive devices in electronic systems can be divided into circuit devices and connecting devices according to their circuit functions.
1. Circuit equipment
(1) diode
(2) resistor
(3) Resistance network
(4) Capacitor
(5) sensor
(6) Transformer
(7) relay
(8) keys
(9) Buzzer and speaker
(10) switch
2. Connected devices
(1) connector
(2) shoket
(3) Connecting cables (wires)
(4) Printed circuit board
2. Common active electronic devices
Active devices are the main devices in electronic circuits. From the physical structure, circuit function and engineering parameters, active devices can be divided into two categories: discrete devices and integrated circuits.
1. discrete device
(1) bipolar transistor, usually called triode, BJT.
(2) field effect transistor.
(3) Thyristors, also called silicon controlled rectifiers.
(4) Semiconductor resistors and capacitors-resistors and capacitors manufactured by integrated processes in integrated circuits.
2. Analog integrated circuit devices
Analog integrated circuit devices are integrated circuit devices used to process analog voltage or current signals that change continuously with time.
Basic analog integrated circuit devices usually include:
(1) integrated operational amplifier.
(2) Comparator
(3) Logarithmic and exponential amplifier
(4) Analog Multiplier/Divider
(5) Analog switch circuit
(6) PLL circuit (phase locked loop), that is, phase locked loop circuit.
(7) Integrated voltage regulator
(8) Reference sources
(9) Waveform generator
(10) power amplifier
3. Digital integrated circuit devices
(1) basic logic gate circuit
(2) Trigger
(3) Registration
(4) Decoder
(5) Data comparator
6. Drivers
(7) Counter
(8) shaping circuit
(9) Programmable logic devices
(10) microprocessor
(1 1) microcontroller
(12) digital signal processor (DSP)
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Active element: An element that can perform data operation and processing between circuit elements.
Including transistors, integrated circuits, picture tubes, displays and other chips in semiconductor devices, are all active components.
Passive components: circuit components that do not affect the basic characteristics of the signal and only allow the signal to pass through without changing it.
The most common are resistors, capacitors, inductors and transformers.
The so-called passive components can operate without electricity, and have the functions of adjusting current and voltage, storing static electricity, preventing electromagnetic wave interference, filtering current impurities and so on.
Compared with active components, the resistance and impedance of passive components will not change when the voltage changes.
Passive components can cover three types of products: resistors, inductors and capacitors.
The following are introduced respectively:
1 resistor: the function of resistor is to adjust the voltage and current in the circuit, which can be divided into three categories according to the material and product packaging.
1. 1 fixed chipless resistor: this product is mainly used for processing power or signals, and electronic products such as power suppliers and monitors are in the greatest demand.
Application: power supply, monitor
1.2 fixed chip resistor: These resistor products are widely used in information, communication, consumer electronics and various instruments.
Applications: information, communication, consumer electronics and various instruments.
1.3 thermistor and variable resistor: mainly used for temperature sensing or control, motor protection and starting devices, and overcurrent/voltage protection devices.
Application: temperature sensing or control, motor protection and starting device, overcurrent/voltage protection device 2 capacitor: when two conductive substances are separated by a medium, it is a capacitor used to store static electricity that may be generated. There are many kinds of capacitors, which can be divided into more than 30 kinds according to the materials used, while domestic manufacturers mainly produce aluminum electrolytic capacitors, ceramic capacitors and plastic film capacitors. Among them, what investors often see in reports is a ceramic capacitor-MLCC. Ceramic capacitors can be basically divided into two categories, one is single-layer ceramic capacitors, and the other is multi-layer ceramic capacitors (MLCC). Because of its small size, large relative capacitance, low loss and high stability in high frequency use, MLCC has broad prospects in dealing with light and short electronic products, and is mainly used in motherboards, notebook computers, mobile phones, scanners, CD-ROMs, modems and so on.
Application: Motherboard, notebook computer, mobile phone, scanner, CD-ROM and modem 3 Inductors: The ability of a coil to store energy in a magnetic field is called an inductor, and this coil is called an inductor. The main function of inductance is to prevent the interference of electromagnetic waves and filter the noise in current, which is widely used. However, the technology and scale of chip inductor production in China are still insufficient, and there is no professional inductor manufacturer.
Applications: Motherboard, personal computer (PC), scanner, power supply, monitor, switch, telephone, modem, various audio-visual equipment.