0
Zener diodes are a form of semiconductor diode that are widely used in electronics circuits as voltage references. Zener diodes provide a stable and defined voltage and as a result Zener diode circuits are often used in power supplies when regulated outputs are needed. Zener diodes are cheap and they are also easy to use and as a result they are used in many applications and many circuits.
Wiki User
∙ 13y ago
Add your answer:
Earn +20 pts
Why current flow from cathode to anode in zener diode?
First off, I don't know if by current flow you mean conventional current flow or electron current flow. You realize they are in opposite directions and most electronics engineers use conventional current flow in circuit analysis.Ignoring this, I will assume your real question is "Why does current flow backwards in zener diodes compared to ordinary diodes?" The answer is that zener diodes are not operated in the forward biased range as are ordinary diodes, instead they are operated in the reverse biased range. When reverse biased enough any diode reaches breakdown voltage and suddenly conducts. Most ordinary diodes can be destroyed by breakdown, but zener diodes are designed to tolerate it. In zener diodes, this breakdown is referred to as "zener breakdown" and the voltage it happens at the "zener voltage".Low voltage zener diodes can still be used in the forward biased mode, like ordinary diodes. However most high voltage zener diodes have a "blocking diode" that is not documented on the data sheet to block forward biased operation. "Blocking diodes" are simply ordinary diodes wired in series with the zener; when the zener would be forward biased they are reverse biased (and thus blocking current), when the zener would be reverse biased they are forward biased.
Can you use zener diode for rectification purpose?
Yes **************************************** Yes they can but there are pitfalls. A normal diode will have a high reverse breakdown voltage. A zener has a relatively low breakdown voltage (its "zener"voltage). If a zener diode is used as a rectifier it must have a zener voltage at least twice the peak of the applied a.c.
When current through a zener diode increases by a factor of 2 by what factor does the voltage across the zener diode increase?
If the zener diode is in zener breakdown the voltage across the zener diode remains constant regardless of current (for the ideal zener diode). Real zener diodes have parasitic resistance that causes the voltage across the zener diode to increase slightly with increased current, but due to temperature dependant variations in this parasitic resistance as well as temperature dependant variations in the zener breakdown voltage, this change in voltage in real zener diodes cannot be described by a simple linear factor.
Zener Regulation with a varying load?
Zener diodes attempt to keep terminal voltage constant. If the load is fairly small, a single zener diode can be used for this purpose. If the load is large enough that the zener cannot hold the voltage within desired margins, I suggest using the zener to control the base of a power transistor; the emitter or collector (depending on transistor type) will be used as the output to the load.
What is the purpose of connecting two zener diodes back to back?
The back to back connected zener diodes can be used as an AC regulator producing what is jokingly called a "poor man's square wave generator". Using this arrangement we can clip the waveform between a positive value of +8.2V and a negative value of -8.2V for a 7.5V zener diode. If we wanted to clip an output waveform between different minimum and maximum values for example, +8V and -6V, use would simply use two differently rated zener diodes. http://www.electronics-tutorials.ws/diode/diode_7.html
Why current flow from cathode to anode in zener diode?
First off, I don't know if by current flow you mean conventional current flow or electron current flow. You realize they are in opposite directions and most electronics engineers use conventional current flow in circuit analysis.Ignoring this, I will assume your real question is "Why does current flow backwards in zener diodes compared to ordinary diodes?" The answer is that zener diodes are not operated in the forward biased range as are ordinary diodes, instead they are operated in the reverse biased range. When reverse biased enough any diode reaches breakdown voltage and suddenly conducts. Most ordinary diodes can be destroyed by breakdown, but zener diodes are designed to tolerate it. In zener diodes, this breakdown is referred to as "zener breakdown" and the voltage it happens at the "zener voltage".Low voltage zener diodes can still be used in the forward biased mode, like ordinary diodes. However most high voltage zener diodes have a "blocking diode" that is not documented on the data sheet to block forward biased operation. "Blocking diodes" are simply ordinary diodes wired in series with the zener; when the zener would be forward biased they are reverse biased (and thus blocking current), when the zener would be reverse biased they are forward biased.
Diodes are commonly used for?
diodes are commonly used for rectification
Zener diodes are mainly used for?
Zener diodes are mainly used as voltage sources. Since they provide a reasonably constant voltage drop, even when current changes, they are useful in small power supplies as voltage regulators.
Can you use zener diode for rectification purpose?
Yes **************************************** Yes they can but there are pitfalls. A normal diode will have a high reverse breakdown voltage. A zener has a relatively low breakdown voltage (its "zener"voltage). If a zener diode is used as a rectifier it must have a zener voltage at least twice the peak of the applied a.c.
Why a zener diode is better than a simple diode?
A typical diode functions only in one direction (forward-bias). When subjected to reverse-bias, the junction will eventually break down under high enough voltage. A zener diode works the same way, but breaks down at a very specific reverse-bias voltage. This is called its zener voltage. Because of this property, a zener diode can be used to regulate the voltage in a circuit. When inserted the opposite orientation as you typically expect a diode, it begins to conduct when the voltage across it reaches the zener voltage. Then the voltage stays at that level. See http://en.wikipedia.org/wiki/Zener_diode for more information.
When current through a zener diode increases by a factor of 2 by what factor does the voltage across the zener diode increase?
If the zener diode is in zener breakdown the voltage across the zener diode remains constant regardless of current (for the ideal zener diode). Real zener diodes have parasitic resistance that causes the voltage across the zener diode to increase slightly with increased current, but due to temperature dependant variations in this parasitic resistance as well as temperature dependant variations in the zener breakdown voltage, this change in voltage in real zener diodes cannot be described by a simple linear factor.
Zener Regulation with a varying load?
Zener diodes attempt to keep terminal voltage constant. If the load is fairly small, a single zener diode can be used for this purpose. If the load is large enough that the zener cannot hold the voltage within desired margins, I suggest using the zener to control the base of a power transistor; the emitter or collector (depending on transistor type) will be used as the output to the load.
Basic construction of zener diode?
A zener diode has a heavily doped p-n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material, such that the reverse voltage is "clamped" to a known value, called the zener voltage.
What is the purpose of connecting two zener diodes back to back?
The back to back connected zener diodes can be used as an AC regulator producing what is jokingly called a "poor man's square wave generator". Using this arrangement we can clip the waveform between a positive value of +8.2V and a negative value of -8.2V for a 7.5V zener diode. If we wanted to clip an output waveform between different minimum and maximum values for example, +8V and -6V, use would simply use two differently rated zener diodes. http://www.electronics-tutorials.ws/diode/diode_7.html
What is the difference between p n junction and zener diode?
The difference between the pn-junction diode and the zener diode is that the pn-junction diode is used for rectification while the zener diode is used for rectification and stabilization. Also, the zener diode can function in the breakdown region while the pn-juntion diode can not function in that regime.
How Zener diode can be used as a reference voltage source?
Zener diodes only allow reverse-biased currents of above a certain (breakdown) voltage. You can use it to test if a current has a voltage above or below a specific number of volts.
Why zener diode used as voltage regulator?
It has a very sharp reverse breakdown voltage curve and is not damaged by the reverse current, as some normal diodes might be.
