Comparison of zener diodes and varistors that belong to semiconductor devices

Semiconductor devices are constructed of materials that are neither good conductors nor good insulators, known as semiconductors, and such devices have established a wide range of applications due to their reliability, compactness, and low cost. They are all discrete components used in power devices, compact optical sensors, and light emitters, including solid-state lasers.

Semiconductor devices with a wide range of current and voltage handling capabilities, with current ratings in excess of 5.000 amperes and voltage ratings in excess of 100.000 volts. What's more, semiconductor devices are suitable for integration into complex but easy-to-build microelectronic circuits. Additionally, semiconductor devices have the potential to be key elements of most electronic systems, including communications with data processing, consumer and industrial control equipment.

A semiconductor device is an electronic device whose conductivity is between a good conductor and an insulator. It utilizes the special electrical characteristics of semiconductor materials to complete specific functions. Semiconductor devices use different semiconductor materials, different processes and geometric structures to develop a wide variety, Electronic components with various functional uses. Semiconductor devices are nothing but electronic components that utilize the electronic properties of semiconductor materials such as silicon, germanium, and silicon, as well as organic semiconductors. Semiconductor devices have replaced vacuum tubes in many applications. They use solid-state electron conduction instead of thermionic emission in high vacuum. Semiconductor devices are manufactured for discrete devices and integrated circuits, which consist of several to billions of devices fabricated and connected on a single semiconductor substrate or wafer. Broadly speaking, there are many classifications of semiconductor devices, including discrete devices, optoelectronic semiconductors, logic ICs, analog LCs, and integrated circuits.

Common electronic components like zener diodes, varistors, etc. are semiconductor devices. Zener diode and varistor, which are both semiconductor devices, which one is more powerful? Since Zener diodes and varistors have different working principles, their functions and applications are also different.

Zener diode

Zener diodes, also known as Zener diodes, are made of semiconductor silicon materials and belong to semiconductor devices. They use PN junctions to reverse breakdown, and their current can vary in a wide range while the voltage remains basically unchanged, which has a voltage stabilizing effect.

Zener diode is a kind of diode, P-type semiconductor and N-type semiconductor are fused together to form a PN junction, and around the PN junction, a depletion layer with anti-phase ions is formed.

There are 2 main differences between Zener diodes and simple diodes:

1. The degree of doping, the simple diode is moderately doped, and the Zener diode is heavily doped to achieve a higher breakdown voltage. The degree of doping is different which contributes to the specification that they work at different voltage levels.

2. In terms of conductivity, due to the high doping of Zener diodes, compared with the PN junction of simple diodes, the depletion layer of Zener diode PN junctions is very thin, which provides special characteristics for Zener diodes. conduction under biased conditions.

Principle of operation

A diode is normally unidirectional with forward conduction and reverse cutoff. However, if the reverse voltage added to the diode exceeds the diode's tolerance, the diode will be damaged by breakdown.

But there is a kind of diode, its forward characteristics and ordinary diode the same, the reverse characteristics are more special: reverse voltage added to a certain extent, the diode shows breakdown, the larger current through the diode will not be damaged, the diode shows breakdown, although the voltage flowing through the diode is very large, but the voltage across the diode is very small, play a role in regulating the diode, this special diode is called a voltage regulator diode. This special diode is called a voltage regulator diode. It is used for regulating power supplies according to its voltage stabilizing characteristics, and it is mainly used as a voltage regulator or voltage reference element in circuits.

A Zener diode acts like a normal diode when forward biased. Then, once the reverse voltage is equal to its rated voltage, it allows current to flow in the reverse direction.

A Zener diode in breakdown operation acts as a voltage regulator because it maintains an almost constant voltage across its terminals over a specified range of reverse current values, which is equal to the Zener voltage. The constant voltage drop across the Zener diode produced by reverse breakdown is indicated by the DC voltage symbol.

Varistor

The varistor is a special resistance device with nonlinear volt-ampere characteristics. The English name is Voltage Dependent Resistor, abbreviated as VDR, or Varistor.

Varistor is not a real resistor, but a component with transient voltage suppression function. Generally, there is no positive and negative poles. This is different from TVS. When used, it is also connected in parallel with the protected IC or circuit. Varistor The response time of the resistor will be a bit slower than the TVS.

When the voltage applied to the varistor exceeds a certain value, its resistance will drop rapidly to conduct a large current and protect the back-end circuit; when it is lower than its operating voltage, the resistance of the varistor is extremely high, which is equivalent to It is open circuit and does not affect the working state of the back-end circuit.

Although the varistor can absorb a large surge energy, it cannot withstand the continuous current above the milliampere level, which must be taken into account when used as overvoltage protection.

The varistor is a new type of voltage-limiting protection element. It is made of semiconductor materials and has nonlinear volt-ampere characteristics. Its resistance is sensitive to voltage. Within a certain current and voltage range, the resistance of the varistor increases with the voltage change with change.

working principle

When the threshold of the varistor itself is greater than the voltage applied externally to the varistor, the current passing through the varistor is extremely small, and the varistor is in an off state at this time.

When the external voltage applied to the varistor is greater than the threshold value of the varistor, the current through the varistor increases and the resistance value decreases. At this time, the varistor is in a closed state, which reduces the influence of the voltage on the circuit, thereby protecting Other electronic components are often used for power overvoltage protection and lightning protection.

The varistor is a voltage limiting protection device. Utilizing the nonlinear characteristics of the varistor, when the overvoltage appears at both ends of the nonlinear varistor, the varistor can clamp the voltage at a relatively fixed voltage value, thereby realizing the protection of the subsequent circuit. Understanding of the specific implementation process: When the voltage applied across the varistor is lower than its threshold voltage, the current flowing through it is extremely small, which is equivalent to a resistor with infinite resistance. That is to say, when the voltage applied to it is lower than its threshold, it acts as an open switch. When the voltage applied across the varistor is higher than its threshold voltage, the current flowing through it increases sharply, which is equivalent to a resistor with infinitesimal resistance. That is to say, when the voltage applied to it is higher than its threshold, it is equivalent to a closed switch.

Summarize

Zener diodes and varistors play an important role in their respective applications due to their own characteristics. The same is true for other electronic components, which can only play their own role when they are used in suitable occasions.

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