1. Resistor

Resistors can be said to be the most commonly used electronic components in circuit engineering, represented by R, which characterizes the obstruction of current by a conductor. Its main functions in a circuit are current division, current limiting, voltage division, and biasing.

Identification of resistor parameters: commonly used methods include color code, value marking, and numerical marking.

The commonly used method is the color code method, where the first and second rings represent the first two digits of the resistance value; the third ring represents the multiplier; and the fourth ring represents the tolerance. For example, when the four color rings are yellow, orange, red, and gold, since the third ring is red, the resistance value is in the range of several kΩ. Substituting the numbers represented by yellow and orange, which are "4" and "3", the reading would be 4.3 kΩ. The gold ring indicates a tolerance of 5%.

2. Capacitor

Capacitors are used in circuits to store charge and electrical energy, represented by C. The main characteristic of a capacitor is that it allows AC to pass while blocking DC. The opposition to AC is called reactance, which is a type of impedance (the other type is inductive reactance). The magnitude of reactance is related to the frequency of the AC and its own capacitance. The main functions of capacitors in circuits are coupling, filtering, resonance, bypassing, compensation, and frequency division.

The parameter representation of capacitors also includes direct marking, text and symbol combination, and color code.

Its model consists of four parts, which does not apply to varistors, variable capacitors, and vacuum capacitors, representing name, material, classification, and serial number respectively.

The classification of capacitors is quite complex. According to current statistical analysis, there are 10 classification methods, which can be referred to in the device manual.

Currently, there is research on supercapacitors, which are capacitors with a capacitance of thousands of farads, using the double-layer principle and activated carbon porous electrodes.

3. Crystal Diode

A semiconductor device with nonlinear volt-ampere characteristics, represented by D, mainly serves the purpose of unidirectional conductivity. The core part is a PN junction, widely used in various electronic circuits. There are many types, classified by material into silicon and germanium; by function into rectifying, light-emitting, detection, voltage regulation, switching, sustaining, Schottky diodes, and silicon power diodes. They can also be classified by structure into point contact and planar types. The former can handle small currents, while the latter can handle large currents.

The main parameters of diodes include maximum rectified current IF, maximum reverse working voltage, reverse current, dynamic resistance, maximum operating frequency, and voltage temperature coefficient.

A diode has two terminals: the positive terminal A is called the anode, and the negative terminal K is called the cathode. Current can only flow from the anode to the cathode. Many beginners confuse diodes with semiconductors; in fact, diodes and semiconductors are completely different, and it can only be said that a diode is a type of semiconductor device.

Identification of diodes: The N pole (negative pole) of small power diodes is mostly marked with a color ring on the exterior. Some diodes also use specific symbols to indicate the P pole (positive pole) or N pole (negative pole), and some use symbols "P" and "N" to determine the polarity of the diode. The positive and negative terminals of light-emitting diodes can be identified by the length of the leads, with the longer lead being positive and the shorter lead being negative. When measuring a diode with a digital multimeter, connect the red probe to the positive terminal and the black probe to the negative terminal; the resistance measured at this time is the forward conduction resistance of the diode, which is exactly the opposite of the connection method for an analog multimeter.

 

4. Inductor

An inductor is a device that converts electrical energy into magnetic energy for storage, with a structure similar to that of a transformer. Inductors are also known as chokes, reactors, or dynamic reactors, represented by L.

Classification: According to the method of induction, there are self-induction and mutual induction. Small inductors can be directly etched onto PCB boards using a method that lays out a spiral track. Small value inductors can also be manufactured using the same process as transistors in integrated circuits. Regardless of the method used, the most commonly applied circuit is called a "rotor," which exhibits the same characteristics as inductive components using a capacitor and active components.

The characteristics of inductors are exactly opposite to those of capacitors; they have the property of blocking AC while allowing DC to pass smoothly, known as passing DC and blocking AC.

Inductors mainly serve functions such as filtering, oscillation, delay, notch filtering, as well as signal selection, noise filtering, current stabilization, and suppression of electromagnetic interference. The most common function is to form an LC filter together with capacitors.

The main parameters of inductors include inductance, allowable error, quality factor, and distributed capacitance.

 

5. Crystal Transistor

Transistors, formally known as semiconductor transistors, also called bipolar transistors or crystal transistors, are semiconductor devices that control current and are core components of electronic circuits.

Transistors are made on a semiconductor substrate with two closely spaced PN junctions, dividing the entire semiconductor into three parts: the middle part is the base region, and the two side parts are the emitter region and collector region, arranged in either PNP or NPN configuration.

Transistors have a current amplification effect; essentially, a transistor can control a large change in collector current with a small change in base current. This is the most basic and important characteristic of transistors. The ratio of ΔIc/ΔIb is referred to as the current gain of the transistor, represented by the symbol "β". The current gain is a constant value for a specific transistor, but it can vary with changes in base current during operation.

Main parameters include characteristic frequency FT, voltage and current, gain, saturation voltage, and power dissipation.

Transistors can operate in cutoff, amplification, and conduction states. The most common use of transistors is to form amplification circuits, with the basic amplification circuit being the most fundamental structure in amplification circuits, serving as the basic unit for constructing complex amplification circuits. It utilizes the characteristic of bipolar semiconductor transistors where the input current controls the output current, or the characteristic of field-effect semiconductor transistors where the input voltage controls the output current, to achieve signal amplification. During amplification, appropriate biasing is required, meaning the emitter junction is forward-biased and the collector junction is reverse-biased. The setup of the input circuit should couple the input signal to the transistor's input electrode, forming a varying base current, thereby generating the current control relationship of the transistor, which translates into changes in collector current. The setup of the output circuit should ensure that the current signal amplified by the transistor is converted into the form of electrical quantity required by the load.

Field Effect Transistor

Field Effect Transistor, abbreviated as FET, is also known as a field effect tube. There are mainly two types: JFET (Junction FET) and MOSFET (Metal-Oxide-Semiconductor FET). It is also called a unipolar transistor, which is a voltage-controlled semiconductor device.

The Field Effect Transistor (FET) is a semiconductor device that uses the electric field effect of the control input circuit to control the output circuit current, hence its name. The FET controls ID (drain current) through VGS (gate-source voltage). In one sentence, the working principle of the FET is: "The ID flowing through the channel between the drain and source is controlled by the reverse-biased gate voltage formed by the pn junction between the gate and the channel."

Function: FETs can be used for amplification. Due to the high input impedance of FET amplifiers, the coupling capacitors can be smaller in capacity, and there is no need to use electrolytic capacitors. The high input impedance of FETs is very suitable for impedance transformation, commonly used in the input stage of multi-stage amplifiers for impedance transformation, can be used as variable resistors, conveniently used as constant current sources, and as electronic switches, etc.

There are two naming methods. The first naming method is the same as that of bipolar transistors, where the third letter J represents junction FET, and O represents insulated gate FET. The second letter represents the material: D is P-type silicon with an N-channel inversion layer; C is N-type silicon with a P-channel. For example, 3DJ6D is a junction P-channel FET, and 3DO6C is an insulated gate N-channel FET. The second naming method is CS××#, where CS represents FET, ×× is a number representing the model number, and # is a letter representing different specifications within the same model. For example, CS14A, CS45G, etc.

FETs have characteristics such as high input impedance, low noise, good thermal stability, and simple manufacturing processes, and are used in large-scale and ultra-large-scale integrated circuits.

Summary

Today, I introduced six commonly used electronic components in electronic circuits, which together form complex circuits.

 

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