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What are the differences between rectifier diodes, voltage regulator diodes, and switch diodes?

What is the difference between rectifier diodes, voltage regulator diodes, and switching diodes? The classification of diode types and diode types can be based on the classification of diode structures, applications, and characteristics

1、 Classification of diode Types and rectifier diode Types: Based on Construction

Semiconductor diodes mainly rely on PN junctions for operation. The point contact type and Schottky type, which are inseparable from PN junctions, are also included in the range of diodes. Based on the characteristics of PN structure, 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 PN junction has a small electrostatic capacity and is 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. Small signal detection, rectification, modulation, mixing, and amplitude limiting are widely used types.

2. Keyed diode

Bond type diodes are formed by fusing or silver filaments onto single crystal germanium or silicon wafers. Its characteristics lie between point contact type diodes and alloy type diodes. Compared to the point contact type, although the PN junction capacity of bond type diodes is slightly higher, their forward characteristics are particularly excellent. It is commonly used as a switch and sometimes also used for detection and power rectification (not exceeding 50mA). In bond type diodes, diodes fused with gold wire are sometimes referred to as gold bond type, while diodes fused with silver wire are sometimes referred to as silver bond type.

3. Alloy diode

PN junctions are formed on single crystal wafers of N-type germanium or silicon by alloying metals such as indium and aluminum. Small forward voltage drop, suitable for high current rectification. Due to its large electrostatic capacity when the PN junction is reversed, it is not suitable for high-frequency detection and rectification.

4. Diffusion diode

In a high-temperature P-type impurity gas, heat a single crystal wafer of N-type germanium or silicon to change a portion of the surface of the wafer into a P-type, and use this method to form a PN junction. Due to the small forward voltage drop of PN junction, it is suitable for high current rectification. Recently, the mainstream of using high current rectifiers has shifted from silicon alloy type to silicon diffusion type.

5. Mesa diode

Although the production method of PN junction is similar to diffusion type, only the necessary parts of PN junction are retained, and the unnecessary parts are corroded off with drugs. The remaining part takes on a surface shape, hence its name. The initial production of the tabletop type was made using diffusion method for semiconductor materials., This type of tabletop is also known as the diffusion tabletop. It seems that there are very few product models for high current rectification, while there are product models for low current switches.

6. diode for amplification

Amplification using diodes generally relies on negative resistive devices such as tunnel diodes and bulk effect diodes, as well as parametric amplification using varactor diodes., Amplification diodes usually refer to tunnel diodes, bulk effect diodes, and varactor diodes

7. diodes for switches

There are logic operations used at low currents (10mA) and switching diodes used for magnetic core excitation at hundreds of milliamps. Low current switching diodes typically include point contact and bond type diodes, as well as silicon diffusion type, mesa type, and planar type diodes that operate at high temperatures. The specialty of switching diodes is their fast switching speed. The switching time of Schottky type diodes is particularly short, due to the ideal switching diode. 2AK type point contact is used for medium speed switch circuits; 2CK type planar contact is used for high-speed switching circuits; Used for circuits such as switching, limiting, clamping, or detection; Schottky (SBD) silicon high current switch with small 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 a name. By applying a reverse voltage,

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

9. diode for frequency multiplication

For the frequency doubling effect of diodes, there are frequency doubling relying on varactor diodes and frequency doubling relying on step (i.e. sudden change) diodes. The variable capacitance diode used for frequency multiplication is called a variable reactor. Although the working principle of the variable capacitance diode used for automatic frequency control is the same, the structure of the reactor can withstand high power. Step diode, also known as step recovery diode, has a short reverse recovery time TRR when switching from on to off, but its specialty is the significantly shorter transition time when rapidly turning off. Applying a sine wave to a step diode can generate high-frequency harmonics due to the short transfer time (tt) and the sudden interruption of the output waveform.

2、 Classification of Diode Types and Diode Types: Based on Purpose

1. diode for detection

In principle, extracting the modulation signal from the input signal is called demodulation, and the output current less than 100mA is usually referred to as demodulation based on the magnitude of the rectification current (100mA) boundary. Germanium material is 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. Diodes used for detection, similar to point contacts, are 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 in characteristics specifically designed for frequency modulation and demodulation. 2. Rectifier diode

In principle, the direct current obtained from the input AC is a rectification. The output current greater than 100mA is usually referred to as rectification based on the magnitude of the rectification current (100mA) boundary. Surface junction type, operating frequency less than KHz, with a maximum reverse voltage ranging from 25 volts to 3000 volts, ranging from A to X in a total of 22 gears. The classification is as follows:

① Silicon semiconductor rectifier diode 2CZ type

② Silicon bridge rectifier QL type

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

3. Limiting diode

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

4. Modulation diode

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

5. diode for mixing

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

6. diode for amplification

7. diodes for switches

8. Varactor diode

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

9. Diode for frequency multiplication

10. Zener diode

It is a product that replaces voltage regulator electronic diodes. It is made into a diffusion type or alloy type of silicon. It is a diode with a sudden change in the reverse breakdown characteristic curve. Made by controlling voltage and using 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 at intervals of 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, it is a 2CW type; If two complementary diodes are connected in reverse series to reduce the temperature coefficient, it is a 2DW type.

11. PIN diode

This is a crystal diode with a layer of Intrinsic semiconductor (or semiconductor with low concentration of impurities) sandwiched between P and N regions. The I in PIN is in the meaning of 'intrinsic'

12. Avalanche diode

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

13. Tunnel diode

It is a crystal diode with tunnel effect current as the main current component. Its substrate materials are gallium arsenide and germanium. The N-type region of its P-type region is highly doped (i.e. with high concentration of impurities). The tunnel current is generated by the quantum mechanical effects of these degenerate state semiconductors. There are three conditions for tunneling effect: ① Fermi energy level is located in 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 region and N-type region of Degenerate semiconductor overlap at the same energy level. The Jiangqi diode is a dual terminal active device. Its main parameters include 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 bands), as well as in high-speed switching circuits.

14. Step Recovery Diode

It is also a diode with a PN junction. The structural feature is that there is a steep impurity distribution area at the PN junction boundary, forming a "self-service electric field". Under the forward bias voltage, the PN junction conducts with a few carriers, and has a charge storage effect near the PN junction, so that its reverse current can be reduced to the minimum value (reverse Saturation current value) after a "storage time". The "self-help electric field" of the step recovery diode shortens the storage time, quickly shuts off the reverse current, and generates rich harmonic components. These harmonic components can be designed as comb shaped 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 known as a "metal semiconductor junction". Its forward starting voltage is relatively low. In addition to materials, the metal layer also uses materials such as gold, molybdenum, nickel, and titanium. Its semiconductor material is silicon or gallium arsenide, mostly N-type semiconductor. This device is conducted by most carriers, and its reverse Saturation current is much larger than that of PN junction conducted by a few carriers. The storage effect of minority carriers in Schottky diodes is very small, 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 energy

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 timing voltage readout circuits. It has the advantages of easy frequency adjustment and good temperature stability.

19. LED

It is made of Gallium phosphide and phosphorus gallium arsenide materials, small in size, and positively driven to emit light. Low working voltage, low working current, uniform light emission, long life, red, yellow and green Monochromatic radiation light.

3、 Classification of diode types and types: based on characteristics

Point contact diodes are classified according to their forward and reverse characteristics as follows.

1. Using point contact diodes

This type of diode, as the title suggests, is commonly used in detection and rectification circuits and is a product with neither particularly good nor bad forward and reverse characteristics. For example, SD34, SD46, 1N34A, etc. belong to this category.

2. High reverse voltage withstand point contact diode

It is a product with high maximum peak reverse voltage and maximum DC reverse voltage. Used for detection and rectification in high-voltage circuits. This type of diode has poor forward characteristics. In point contact germanium diodes, there are SD38, 1N38A, OA81, and so on. This type of germanium material diode has limited voltage resistance. At higher temperatures, there are silicon alloys and diffusion types.

3. High reverse resistance point contact diode

Forward voltage characteristics and diode usage. Although its reverse direction withstand voltage is also particularly high, the reverse current is small, and its specialty is high reverse resistance. In circuits with high input resistance and high resistance load resistance, SD54, 1N54A, and other germanium materials with high reverse resistance type diodes belong to this category of diodes.

4. High conductivity point contact diode

It is the opposite of the high reverse resistance type. Its reverse characteristics are poor, but the forward resistance is small enough. For high conductivity bond type diodes, better characteristics are obtained. This type of diode has higher rectification efficiency when the load resistance is particularly low