Schottky Diodes How Schottky Diodes Work

The Schottky diode is a hot carrier diode. Schottky diodes are also known as Schottky barrier diodes, which are low-power, ultra-high-speed semiconductor devices. Schottky diodes are widely used in circuits such as inverters, switching power supplies, and drivers as low-voltage, high-frequency, High-current rectifier diodes, protection diodes, freewheeling diodes, etc., Schottky diodes used in microwave communications and other circuits for rectifier diodes, small signal detection diodes. What is the role of a Schottky diode ? What are the specific roles of the diodes ? The following is an introduction to Schottky diodes.

Schottky diode advantages

Schottky diodes have the advantages of high switching frequency, reduced forward voltage, etc., but the reverse breakdown voltage of Schottky diodes is relatively low, generally not higher than 60V, and the highest is only about 100V, which limits Schottky. The application range of the diode. High-frequency rectifier diodes with a voltage of 100V or more, switching power supplies and power factor correction circuits in the secondary of the transformer, freewheeling diodes in RCD snubber circuits, high-speed diodes between 600V and 1.2kV, and 600V for PFC boost. In the case of diodes, etc., only use fast recovery epitaxial diodes and ultrafast recovery diodes. Today's Schottky diodes have made breakthrough progress. 150V and 200V high voltages are already on the market, and Schottky diodes using new materials have also been successfully developed.

The working principle of the diode

The working principle of the diode (forward conduction, reverse conduction)

A crystal diode is a pn junction formed by a p-type semiconductor and an n-type semiconductor. A space charge layer is formed at both sides of the interface and a self-built electric field is built. When there is no applied voltage, the pn junction has two side carriers. The diffusion current caused by the difference in concentration is equivalent to the drift current caused by the self-built electric field and is in an electrically balanced state. When a forward voltage bias occurs, the mutual suppression of the external electric field and the self-built electric field increases the diffusion current of the carrier and causes a forward current. (that is, the cause of conduction) When a reverse voltage bias is generated, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current that is independent of the value of the reverse bias voltage in a certain reverse voltage range. (This is also the cause of nonconductivity.) The crystal diode is a pn junction formed of a p-type semiconductor and an n-type semiconductor. A space charge layer is formed on both sides of the crystal diode, and a self-built electric field is built when there is no applied voltage. The diffusion current caused by the difference in carrier concentration on both sides of the pn junction is equal to the drift current caused by the self-built electric field and is in an electric equilibrium state. When the outside world is biased by the forward voltage, mutual suppression of the external electric field and the self-built electric field increases the diffusion current of the carrier and causes a forward current.

When the outside world has a reverse voltage bias, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current I0 independent of the reverse bias voltage value within a certain reverse voltage range.

When the applied reverse voltage is high to a certain extent, the electric field intensity in the space charge layer of the pn junction reaches a critical value to generate a doubled charge carrier process, generating a large number of electron-hole pairs, resulting in a large reverse breakdown current This is called the diode breakdown phenomenon.

  

The role of the diode

1, rectification

By using the unidirectional conductivity of the diode, it is possible to convert alternately alternating alternating currents into a single direction pulsed direct current.

2, switch

The resistance of the diode under the forward voltage is very small and it is in the conducting state, which is equivalent to a switch that is turned on. Under the action of the reverse voltage, the resistance is very large and is in the cut-off state, like an open switch. Using the switching characteristics of the diodes, various logic circuits can be formed.

3, limiter

After the diode is conducting, its forward voltage drop remains essentially unchanged (0.7V for silicon and 0.3V for neon). Using this feature, as a limiting element in the circuit, the signal amplitude can be limited to a certain range.

4, free flow

In the switching power supply inductance and relays and other inductive load play a freewheeling role.

5, detection

Plays a wave on the radio.

6, change the volume

Used in the tuner of the TV.

7, display

For VCDs, DVDs, calculators and other displays.

8, regulator

The zener diode is essentially a junction-type silicon diode, and the zener diode operates in a reverse breakdown state. In the manufacturing process of the diode, it has low voltage breakdown characteristics. The reverse breakdown voltage of the zener diode is constant, and the current limiting resistor is serially connected in the voltage stabilizing circuit so that the current does not exceed the allowable value after the voltage regulator tube is punctured, so the breakdown state can be sustained for a long time and will not be damaged.

9, trigger

The trigger diode, also known as a two-way trigger diode (DIAC), is a three-layer structure with symmetrical two-terminal semiconductor devices. Commonly used to trigger triac, for overvoltage protection in the circuit and other purposes.

  

The role of Schottky diodes

Schottky is named after its inventor Dr. Schottky, which is an abbreviation of Schottky Barrier Diode (abbreviated as SBD). SBD is not made by the principle of forming a PN junction by the contact of a P-type semiconductor and an N-type semiconductor, but is based on the principle of a metal-semiconductor junction formed by the contact of a metal and a semiconductor. Therefore, SBD is also called a metal-semiconductor (contact) diode or a surface barrier diode, which is a kind of hot carrier diode.

It is a low-power, ultra-high-speed semiconductor device widely used in circuits such as switching power supplies, inverters, and drivers for high-frequency, low-voltage, high-current rectifier diodes, freewheeling diodes, and protection diodes, or in microwave communications, etc. The circuit is used as a rectifier diode and a small signal detection diode.

Schottky diode features

Since the Schottky diode-based barrier height is lower than the PN junction barrier height, both the forward conduction threshold voltage and the forward voltage drop of the Schottky diode are lower than those of the PN junction diode. Since the Schottky diode is a majority carrier conduction device, there are no problems such as minority carrier lifetime and reverse recovery. The reverse recovery time of the Schottky diode is only the charge and discharge time of the Schottky barrier capacitor, which is completely different from the reverse recovery time of the PN diode. Because Schottky diodes have less reverse recovery charge, Schottky diodes have extremely fast switching speeds and minimize switching losses, making them particularly suitable for high frequency applications.

Schottky diode applications

The structure and characteristics of the Schottky diode make it suitable for high-frequency rectification in low voltage, high current output applications, etc., and for detection and mixing at high frequencies. Schottky diodes are used as clamps in high-speed logic circuits. . Schottky diodes are also commonly used in ICs and are widely used in high-speed computers. In addition to the characteristic parameters of ordinary PN junction diodes, the Schottky diode's electrical parameters for detection and mixing also include intermediate frequency impedance, which refers to the impedance that the Schottky diode presents to the specified intermediate frequency when the rated local oscillator power is applied. The above is Xiaobian's specific introduction to Schottky diodes. I hope that we can learn from them.

Editor's summary: The above is the role of Schottky diodes. The working principle of Schottky diodes is related to whether or not you have a further understanding of Schottky diodes. If you still want to learn more about the relevant information, please continue to follow our website.

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