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PCBA / Circuit Board / DIP plug-in /
post-soldering Processing
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PCBA / Circuit Board / DIP plug-in /
post-soldering Processing
The semiconductor industry is one of the most important and diverse among industries. It has been constantly evolving since the invention of the transistor. Although the transistor was found to be the perfect replacement for bulbs, it is important to mention that electronics theory was based on the later.
Hence, the main working principles of the transistor and diodes was idealized way before the industry. Therefore, it is of importance to understand that diodes were great elements for protection and signal rectification. In this article we will explore on the Zener diode and understand its properties and characteristics.
When the first diode was invented in 1904, many applications for DC equipment became of importance, since it could rectify, or so to say, AC signals. The fact that the current could only flow in one direction through the diode made it ideal also for isolation in the circuitry and allow signal mixing.
However, it was not until the Zener diode came in 1950 that small amounts of current could flow on the reverse state operation for the Zener diode. It is mainly utilized for applications that require switching or regulation as described below.
A Zener diode has the advantage of dual bias operation, which means that it can rectify as a common diode on forward-bias condition and allow a small leak current to flow on reverse-biased. As some current may leak through the Zener diode, this allows the leak current to be measured with proper instrumentation, making it a very cheap shunt. However, nothing is perfect, and so the power dissipation wasted in the Zener diode.
Although regulation is a huge advantage, power dissipation is to be considered as the element may overheat with huge loads. Additionally, if the nominal current flowing varies, so will the Zener diode’s, consider hysteresis involved at some points. Finally, the output voltage for the Zener diode cannot be regulated due to the intrinsic Zener voltage property involved.
As stated above, Zener diode’s can be connected in reverse-biased condition, this allows them to work for voltage regulation applications. In this case, the main advantage of doing this is cost against using a low drop-out voltage regulator, and in this sense, it is important to state that load should be constant to ensure proper power dissipation. In fact, there are other applications for Zener diode’s which include surge protection and dedicated isolation, but their application is not as popular.
As a diode itself, a Zener diode works as a diode when the current is forward-biased. On the other hand, when the current flows in the opposite direction, current will flow if the breakdown voltage condition is met. These components have a wide range of breakdown voltages, which, in fact, is related to the amount of mineral doping on the component itself as will be described further below.
A Zener diode is diode with a huge level of mineral doping. The nature of this high doping allows the current to flow backwards under reverse-biased mode. There is a thin region known as depletion region, that varies in function of the doping amount, which in fact, results on the variation of the breakdown voltage parameter in a positive dependency, meaning, that the higher the doping, the higher the breakdown voltage value will be.
There are different kinds of diodes, having the normal rectifying diodes, Zener diodes or even Schottky diodes. When to use a specific kind of diode and for what? Remember that doping is low on conventional diodes, which provide utmost reverse current protection. So, in fact, circuits that require complete isolation shall require this type of diode. Hence, the application of conventional diodes is for rectifying circuits while regulation choices will include Zener diodes in essence.
Zener diodes tend to fail when the power cannot be dissipated appropriately through heat, meaning that the package itself has broken or is not capable of working in its desired condition. The failure condition for Zener diodes will be most likely to short the diode. It is due to this condition that they are not suitable for isolation in comparison with conventional rectifier diodes. Once the component started failing, the amount of voltage will drop or is starts falling from its designed breakdown voltage value.
Also read:
Top 15 globally automotive rectifier diode manufacturers
Design limitations for a Zener diode include the maximum amount of current rating for the diode itself and its power dissipation which is related to the diode’s Zener resistance parameter. As temperature rises, so will the internal Zener resistance, and in this case, a voltage stability condition is predefined with specific voltage tolerance properties. So, consider your constant load values and stabilization conditions when utilizing a Zener diode! It is worth mentioning that there are Zener diodes that might contain breakdown voltages up to 1kV!
In a similar fashion as with rectifying diodes, Zener diodes have physical markings or “line” on the cathode, which allows understanding for its proper utilization and placement within a defined circuit.
