What is the difference between rectifier diode, voltage regulator diode, and switch diode?

 The types of diodes and their classification can be distinguished based on the structure, purpose, and characteristics of the diodes

1、 Types of diodes and classification of diode types: Classified by structure

Semiconductor diodes mainly operate by relying on PN junctions. The point contact type and Schottky type, which are inseparable from the PN junction, are also included in the scope of diodes. Based on the characteristics of PN structure surface construction, crystal diodes are classified into the following types, including these two models:

1. Point contact diode

A point contact diode is formed by pressing a metal needle onto a single crystal of germanium or silicon material and then using the current method., The static capacitance of its PN junction is small, making it suitable for high-frequency circuits., Compared with surface junction diodes, point contact diodes have poor forward and reverse characteristics and cannot be used for high current and rectification. Simple construction and affordable price. In terms of the detection, rectification, modulation, mixing, and limiting of small signals, it is a widely used type.

2. Key type diode

A key type diode is formed by fusing or silver filaments onto a single crystal of germanium or silicon. Its characteristics are between point contact diodes and alloy diodes. Compared with the point contact type, although the PN junction capacity of the key type diode is slightly higher, the forward characteristic is

The sex is particularly excellent. Commonly used as a switch, sometimes also applied to detection and power rectification (not greater than 50mA). In key type diodes, diodes with fused gold wires are sometimes referred to as gold bond type, while diodes with fused silver wires are sometimes referred to as silver bond type.

3. Alloy type diode

A PN junction is formed on a single crystal wafer of N-type germanium or silicon by alloying with metals such as indium and aluminum. Small forward voltage drop, suitable for high current rectification. Due to its high static capacitance when the PN junction is reversed, it is not suitable for high-frequency detection and rectification.

4. Diffusion diode

Heating a single crystal of N-type germanium or silicon in a high-temperature P-type impurity gas causes a portion of the surface of the single crystal to become P-type, This method is used for PN junction. Due to the small forward voltage drop of PN junction, it is suitable for high current rectification. Recently, the mainstream use of high current rectifiers has shifted from silicon alloy type to silicon diffusion type.

5. Desktop diode

Although the production method of PN junction is different from diffusion type, only the necessary parts of PN junction are retained, and the unnecessary parts are corroded away with drugs. The remaining part takes on a rectangular shape, hence the name. The initial production of countertops was made using diffusion method on semiconductor materials., This type of tabletop is also called a diffusion tabletop. This type seems to have very few product models for high current rectification, while the product models for low current switches are limited.

6. Planar diode

A PN junction formed by selectively diffusing only a portion of P-type impurities on a semiconductor single crystal wafer (mainly N-type silicon single crystal wafer) and the shielding effect of the oxide film on the surface of the silicon wafer., The drug does not corrode the PN junction area. The semiconductor surface is made flat, hence the name. Moreover, the surface of PN bonding is recognized as a type with good stability and long lifespan due to being covered by an oxide film. Initially, the semiconductor materials used were formed using epitaxial methods, hence the planar type was also referred to as epitaxial planar type. For planar diodes, there seem to be few models used for high current rectification, while models used for low current switching are limited.

7. Alloy diffusion diode

It is a type of alloy. Alloy materials are diffused materials. By cleverly doping difficult to produce materials with impurities, they can diffuse together with the alloy to achieve the appropriate concentration distribution of impurities in the formed PN junction. This method is suitable for manufacturing high-sensitivity varactor diodes.

8. Epitaxial diode

A diode formed by manufacturing a PN junction through the process of extending the surface length. Extremely advanced technology during manufacturing. Due to the ability to freely control the distribution of impurities at different concentrations, it is suitable for manufacturing high-sensitivity varactor diodes.

9. Schottky diode

The basic principle is to use the formed Schottky barrier on the contact surface between metal (such as lead) and semiconductor (N-type silicon wafer) to block reverse voltage. The rectification principles of Schottky and PN junctions have inherent differences. Its withstand voltage is only about 40V. Its strengths are: very fast switching speed and particularly short reverse recovery time trr., Capable of producing switch diodes and low-voltage high current rectifier diodes.

2、 Types of diodes and classification of diode types: Classified by purpose

1. Detection diode

In principle, extracting the modulated signal from the input signal is called detection, and the output current less than 100mA is usually called detection based on the size of the rectified current (100mA). Germanium material is a point contact type with a working frequency of up to 400MHz, low forward voltage drop, small junction capacitance, high detection efficiency, and good frequency characteristics. It is a 2AP type. A diode used for detection, similar to a point touch type, is not only used for detection, but also for limiting, clipping, modulation, mixing, switching and other circuits. There are also two diode assemblies with good consistency of characteristics specifically designed for frequency modulation detection.

2. Rectifier diode

In principle, the DC output obtained from the input AC is rectified. Rectify the output current greater than 100mA based on the magnitude of the rectified current (100mA). Surface junction type, operating frequency less than KHz, with a maximum reverse voltage ranging from 25 volts to 3000 volts divided into 22 levels A to X. The categories are as follows:

① 2CZ type silicon semiconductor rectifier diode

② Silicon bridge rectifier QL type

③ 2CLG type used for high voltage silicon stack of televisions with a working frequency of nearly 100KHz.

3. Limiting diode

Most diodes can be used with limited amplitude. There are also specialized limiting diodes such as protective instruments and high-frequency Zener diodes. These diodes have a particularly strong ability to limit sharp amplitudes, typically using diodes made of silicon materials. Some components are also sold: based on the limited voltage, several necessary rectifier diodes are connected in series to form a whole.

4. Modulation diode

Usually refers to diodes specifically designed for ring modulation. A combination of four diodes with good consistency in forward characteristics. Even though varactor diodes have modulation purposes, they are usually used for direct frequency modulation.

5. Mixing diode

When using diode mixing, Schottky and point contact diodes are commonly used in the frequency range of 500-10000Hz.

6. Amplifying diode

Amplification using diodes can be achieved through negative resistive devices such as tunneling diodes and body effect diodes, as well as parametric amplification using varactor diodes., Amplification diodes usually refer to tunnel diodes, body effect diodes, and varactor diodes.

7. Switching diode

There are logic operations used at low currents (10mA) and switch diodes for magnetic core excitation used at several hundred milliamps. Low current switching diodes usually include point contact and key type diodes, as well as silicon diffusion type, table type, and planar type diodes that operate at high temperatures. The specialty of switch diodes is their fast switching speed. The switching time of Schottky diodes is particularly short, as they are ideal switching diodes. 2AK type point contact is used for medium speed switch circuits; 2CK type planar contact is used for high-speed switch circuits; Used for circuits such as switches, limiters, clamps, or detectors; Schottky (SBD) silicon high current switch has low forward voltage drop, fast speed, and high efficiency.

8. Varactor diode

The low-power diode used for automatic frequency control (AFC) and tuning is called a varactor diode. Japanese manufacturers also have names. By applying a reverse voltage,

Causing a change in the electrostatic capacitance of its PN junction., Used for automatic frequency control, sweep oscillation, frequency modulation, and tuning purposes. Usually, although silicon diffusion diodes are used, special fabricated diodes such as alloy diffusion type, epitaxial bonding type, and double diffusion type can also be used. In terms of voltage, the rate of change in electrostatic capacitance of these diodes is particularly large. The junction capacitor changes with the reverse voltage VR, replacing the variable capacitor, and is used as a tuning circuit, oscillation circuit, phase-locked loop. It is commonly used in the channel conversion and tuning circuit of TV high-frequency heads, and is mostly made of silicon materials.

9. Frequency doubling diode

For the frequency doubling effect of diodes, there are frequency doubling relying on varactor diodes and frequency doubling relying on step (i.e. rapid) diodes. The variable capacitance diode used for frequency doubling is called a variable reactor. Although the variable reactor works on the same principle as the variable capacitance diode used for automatic frequency control, its structure can withstand high power. A step diode, also known as a step recovery diode, has a short reverse recovery time trr when switching from conduction to shutdown. Its advantage is that the transition time to quickly turn off is significantly short. Applying a sine wave to a step diode can generate high-frequency harmonics due to the short transition time (tt) and sudden interruption of the output waveform.

10. Zener diode

It is a product that replaces voltage regulator electronic diodes. Made into a diffusion type or alloy type of silicon. It is a diode with a sudden change in reverse breakdown characteristic curve. Made using controlled voltage and standard voltage. The terminal voltage (also known as Zener voltage) of a diode during operation ranges from around 3V to 150V, and can be classified into levels every 10%. In terms of power, there are also products ranging from 200mW to 100W. Working in reverse breakdown, made of silicon material, with a very small dynamic resistance RZ, of 2CW type; Connecting two complementary diodes in reverse series to reduce the temperature coefficient is a 2DW type.

11. PIN diode

This is a crystal diode constructed by sandwiching an intrinsic semiconductor (or a semiconductor with low concentration impurities) between the P and N regions. The 'I' in PIN is an English abbreviation for 'intrinsic' meaning. When its operating frequency exceeds 100MHz, the storage effect of minority carriers and the transit time effect in the "intrinsic" layer cause the diode to lose its rectification function and become an impedance element, and its impedance value changes with the bias voltage. In zero bias or DC reverse bias, the impedance of the "intrinsic" region is very high; When a DC forward bias is applied, charge carriers are injected into the "intrinsic" region, causing it to exhibit low impedance., Use PIN diode variable impedance components. It is often used in high-frequency switches (i.e. microwave switches), phase shifting, modulation, limiting and other circuits.

12. Avalanche diode

It is a transistor that generates high-frequency oscillations under the action of an external voltage. The working principle of generating high-frequency oscillations is Luan: avalanche breakdown injects charge carriers into the crystal, and the current lags behind the voltage due to the time it takes for the charge carriers to cross the chip. If the transit time is controlled, a negative resistance effect will occur in the relationship between current and voltage, resulting in high-frequency oscillations. It is often applied in oscillation circuits in the microwave field.

13. Tunnel Diode

It is a crystal diode with tunneling effect current as the main current component. The base materials are gallium arsenide and germanium. The N-type region of its P-type region is highly doped (i.e. high concentration of impurities). The tunneling current is generated by the quantum mechanical effects of these degenerate semiconductors. The occurrence of tunneling effect requires the following three conditions: ① the Fermi level is located in the conduction band and full band; ② The width of the space charge layer is very narrow (below 0.01 micrometers); The holes and electrons in the P-type and N-type regions of degenerate semiconductors overlap at the same energy level. Jiangqi diode is a dual terminal active device. Its main parameters are peak to valley current ratio (IP/PV), where the subscript "P" represents "peak"; And the subscript "V" represents "valley". Jiangqi diodes are used in low-noise high-frequency amplifiers and high-frequency oscillators (with operating frequencies up to millimeter wave band), as well as in high-speed switching circuits.

14. Fast turn off (step recovery) diode

It is also a diode with a PN junction. Its structural feature is that it has a steep impurity distribution region at the PN junction boundary, forming a "self electric field". Under forward bias, the PN junction conducts with a small number of charge carriers and has a charge storage effect near the PN junction, causing its reverse current to experience a "storage time" before reaching its minimum value (reverse saturation current value). The "self electric field" of the step recovery diode shortens the storage time, quickly cuts off the reverse current, and generates rich harmonic components. These harmonic components can be designed into comb like frequency spectrum generation circuits. Fast turn off (step recovery) diodes are used in pulse and high-order harmonic circuits.

15. Schottky Barrier Diode

It is a diode with Schottky characteristics and a "metal semiconductor junction". Its forward starting voltage is relatively low. In addition to materials, its metal layer also uses materials such as gold, molybdenum, nickel, titanium, etc. Its semiconductor materials are made of silicon or gallium arsenide, mostly N-type semiconductors. This device is conducted by majority carriers, and its reverse saturation current is much larger than that of PN junctions conducted by minority carriers. The storage effect of minority carriers in Schottky diodes is minimal, and their frequency response is only limited by the RC time constant. Therefore, it is an ideal device for high-frequency and fast switching. Its operating frequency can reach 100GHz. And MIS (metal insulator semiconductor) Schottky diodes are used to make solar cells or light-emitting diodes.

16. Damping diode

High reverse working voltage and peak current, low forward voltage drop, high-frequency high-voltage rectifier diode, used for damping and boost rectification in TV scanning circuits.

17. Transient voltage suppression diode

TVP diode provides fast overvoltage protection for circuits, divided into bipolar and unipolar types, classified according to peak power (500W-5000W) and voltage (8.2V-200V).

18. Double base diode (single junction transistor)

A three terminal negative resistance device with two bases and one emitter, used in relaxation oscillation circuits and timed voltage readout circuits, has the advantages of easy frequency adjustment and good temperature stability.

3、 Types of diodes and classification of diode types: Point contact diodes are classified according to their characteristics, and are classified according to their forward and reverse characteristics as follows.

1. Using point contact diodes

As the title suggests, this type of diode is commonly used in detection and rectification circuits, and is a product with neither particularly good nor particularly bad forward and reverse characteristics.

2. High reverse withstand voltage point contact diode

It is a product with high maximum peak reverse voltage and maximum DC reverse voltage. Used for detection and rectification of high-voltage circuits. This type of diode has poor forward characteristics. In point contact germanium diodes. This germanium material diode has limited voltage resistance. At higher altitudes, there are silicon alloys and diffusion types.

3. High reverse resistance point contact diode

Forward voltage characteristics and the use of diodes. Although its reverse voltage resistance is particularly high, its advantage lies in its high reverse resistance due to its small reverse current. In circuits with high input resistance and high resistance load resistance, germanium material high reverse resistance diodes belong to this type of diode.

4. High conductivity point contact diode

It is opposite to the high reverse resistance type. Its reverse characteristic is poor, but it makes the forward resistance small enough. For high conductivity point contact diodes. For high conductivity key type diodes, better characteristics are obtained. This type of diode has high rectification efficiency when the load resistance is particularly low.