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Zener diodes are manufactured in a variety of packages ranging from small surface mount deceives to large stud mounted

A Zener diode is a type of diode that is frequently employed as a shunt regulator to hold a voltage constant at a pre-determined level. Zener diodes may be constructed as discrete components or embedded into Integrated circuits.

History

A type 2N4735A Zener diode is considerably smaller than the 5651 Voltage regulator tube

Zener diodes were proceeded by Voltage regulator tubes. By comparison to modern zener diodes, the VR tube is considerably larger, delicate, and requires high operating voltages. The accompanying picture illustrates the size difference between a type 5651 voltage regulator tube and a type 1N4735A zener diode.

The zener diode which bears the name of its inventor was developed in the late 1950 by Dr. Clarence Zener while working at Westinghouse Electrical Company ^[1]

The zener diode was further refined in the mid 1970s when National Semiconductor developed the buried-zener diode as featured in the LM199 precision voltage reference.^[1] The buried-zener diode has the advantage of being less electrically noisy than the conventional zener diode.^[2]

Usage

Zener diode as a shunt regulator

The Zener diode may be used as simple shunt regulator. With an appropriate series connected current limiting resistor (R1), the circuit will provide an accurate voltage level independent of changes in either the input power supply (V_S) or changes in the load (R2).

This type of circuit is highly inefficient ^[3]. For a given (V_S) the current is always constant since the Zener diode and load effectively form a current divider i.e., the circuit consumes power even when the load is disconnected^{[citation needed]}. This attribute must be considered when selecting a Zener diode to guard against possible destruction when the load is disconnected.

The resistor R1 supplies the Zener current I_Z as well as the load current I_R2 (R2 is the load). R1 can be calculated as -

$R1={\frac {V_{S}-V_{Z}}{I_{Z}+I_{R2}}}$ where, V_Z is the zener voltage, and I_R2 is the required load current.^{[citation needed]}

Zener diode as a voltage reference

Make distinction between shunt regulation and VR - the Zener may be low power as the external pass element handles the current

Regulated power supplies often contain a Zener Diode as a voltage reference. The output of the power supply (feedback) is compared to the voltage reference in a comparator stage. The comparator then adjusts the output of the power supply to maintain the feedback at the same level as the voltage reference thereby providing regulation.^{[citation needed]} These devices are also encountered, typically in series with a base-emitter junction, in transistor stages where selective choice of a device centered around the avalanche/Zener point can be used to introduce compensating temperature co-efficient balancing of the transistor PN junction. An example of this kind of use would be a DC error amplifier used in a stabilized power supply circuit feedback loop system.

Zener diode as a clamp

Zener diode clamp used to limit the signal to an amplifier

The voltage to a to a sensitive amplifier stage may be limited by using a Zener diode as shown in the accompanying figure.

Zener diode as a noise generator

A white noise generator may be formed using a zener diode and a low noise amplifier

A Zener diode may be used as a wideband white noise generator. ^[4] This white noise is caused when a Zener diode operates in the reverse breakdown mode. A low noise amplifier may be required to boost the signal to a usable level.

Zener diode as a level shifter

An AC signal may passed through a Zener diode.

Specification

The specification for an individual Zener diode are available in the device's data sheet. While each data sheet contains many unique specification, this article will focus on breakdown voltage, power, and the temperature coefficient.

Breakdown voltage

Voltages available (~1 - 100V)
Doping (semiconductor)

Power dissipation

power (~0.25 to 50 W)

The power dissipated by a Zener diode is a product of the voltage drop and amount of current passing through the Zener diode. Consequently, the power rating is largely determined by case style (physical size and the heatsink). A stud mounted device such as the XXXX may dissipate XXX watts while attached to a the specified minimum heatsink Template:Needs ref. The smaller 2N4735A may only disipate XXX wattsTemplate:Needs ref.

The maximum power dissipation is also dependent on the temperature of the device. The Zener diode data sheet will normally present a chart derating the device.

Temperature coefficient

Not applicable to all data sheets
sweet spot at ~6.2VDC

Lead identification

The Zener diode is a two terminal device consisting of a cathode and anode. The cathode is normally identified by a small band on the body of the device. Larger devices may have the schematic symbol of the Zener diode printed on the case. Refer to the manufactures data sheet if there are no identifiable markings.

Theory of operation

Because it is almost always the reverse-breakdown property of the Zener diode that is useful, in circuit schematics the Zener diode symbol (i.e., a diode arrow) typically points in the opposite direction of the circuit's positive current flow. This use is opposite that of a typical diode, which would be aligned with the current flow.

Current-voltage characteristic of a Zener diode with a breakdown voltage of 17 volt. Notice the change of voltage scale between the forward biased (positive) direction and the reverse biased (negative) direction.
A Zener diode is a type of diode that permits current in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as "Zener knee voltage" or "Zener voltage".
A conventional solid-state diode will not allow significant current if it is reverse-biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to avalanche breakdown. Unless this current is limited by external circuitry, the diode will be permanently damaged. In case of large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount of the voltage drop depends on the semiconductor material and the doping concentrations.
A Zener diode exhibits almost the same properties, except the device is specially designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage. A Zener diode contains 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. In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states; as a result of the reduced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on both sides. A reverse-biased Zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the Zener diode at the Zener voltage. For example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of 3.2 V if reverse bias voltage applied across it is more than its Zener voltage. However, the current is not unlimited, so the Zener diode is typically used to generate a reference voltage for an amplifier stage, or as a voltage stabilizer for low-current applications.
The breakdown voltage can be controlled quite accurately in the doping process. While tolerances within 0.05% are available, the most widely used tolerances are 5% and 10%.
Another mechanism that produces a similar effect is the avalanche effect as in the avalanche diode. The two types of diode are in fact constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the Zener effect is the predominant effect and shows a marked negative temperature coefficient. Above 5.6 volts, the avalanche effect becomes predominant and exhibits a positive temperature coefficient.
In a 5.6 V diode, the two effects occur together and their temperature coefficients neatly cancel each other out, thus the 5.6 V diode is the component of choice in temperature-critical applications.
Modern manufacturing techniques have produced devices with voltages lower than 5.6 V with negligible temperature coefficients, but as higher voltage devices are encountered, the temperature coefficient rises dramatically. A 75 V diode has 10 times the coefficient of a 12 V diode.
All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of "Zener diode".

References

^ ^a ^b Harrison, Linden (2005). Current Sources & Voltage Reference, Burlington: Newnes
^ Horowitz, Paul and Hill, Winfield. (1989) The Art of Electronics 2nd Ed., Cambridge: Cambridge University Press
^ ARRL handbook (2006) page 5.19
^ Maxim Application Note 3469 (March 14, 2005) Building a Low-Cost White-Noise Generator.

[Harrison-1] Harrison, Linden (2005). Current Sources & Voltage Reference, Burlington: Newnes

[2] Horowitz, Paul and Hill, Winfield. (1989) The Art of Electronics 2nd Ed., Cambridge: Cambridge University Press

[3] ARRL handbook (2006) page 5.19

[4] Maxim Application Note 3469 (March 14, 2005) Building a Low-Cost White-Noise Generator.

[1]

[2]

[3]

[4]

@@ Line 1: / Line 1: @@
-{{Expand|date=January 2009}}
 [[Image:Zener diode symbol.svg|right|250px|thumb|Zener diode schematic symbol]]
-[[Image:Wiki.png|right|thumb|Zener diodes are manufactured in a variety of packages from small [[surface mount]] deceives to large stud mounted]]
+[[Image:Wiki.png|right|thumb|Zener diodes are manufactured in a variety of packages ranging from small [[surface mount]] deceives to large stud mounted]]
 A '''Zener diode''' is a type of [[diode]] that is frequently employed as a [[Linear regulator | shunt regulator]] to hold a voltage constant at a pre-determined level.  Zener diodes may be constructed as [[discrete components]] or embedded into [[Integrated circuits]].
@@ Line 9: / Line 7: @@
 [[Image:Wiki.png|right|thumb|A type 2N4735A Zener diode is considerably smaller than the 5651 Voltage regulator tube]]
-Zener diodes were proceeded by [[Voltage regulator tube]]s.  By comparison to modern zener diodes, the VR tube is considerably larger, delicate, and requires high operating voltages.  The accompanying picture illustrates the size difference between a type 5651 voltage regulator tube and a type 1N4745A zener diode.
+Zener diodes were proceeded by [[Voltage regulator tube]]s.  By comparison to modern zener diodes, the VR tube is considerably larger, delicate, and requires high operating voltages.  The accompanying picture illustrates the size difference between a type 5651 voltage regulator tube and a type 1N4735A zener diode.
 The zener diode which bears the name of its inventor was developed in the late 1950 by Dr. [[Clarence Zener]] while working at Westinghouse Electrical Company <ref name="Harrison"> Harrison, Linden (2005). ''Current Sources & Voltage Reference'', Burlington: Newnes </ref>
@@ Line 15: / Line 13: @@
 The zener diode was further refined in the mid 1970s when [[National Semiconductor]] developed the [[buried-zener diode]] as featured in the LM199 precision voltage reference.<ref name = "Harrison"/>  The buried-zener diode has the advantage of being less [[electronic noise |electrically noisy]] than the conventional zener diode.<ref> Horowitz, Paul and Hill, Winfield. (1989) ''The Art of Electronics 2nd Ed.'', Cambridge: Cambridge University Press </ref>
+==Usage==
-== Theory of operation==
-{{Unreferenced|date=December 2006}}
-[[Image:V-a characteristic Zener diode.svg|thumb|250px|Current-voltage characteristic of a Zener diode with a breakdown voltage of 17 volt. Notice the change of voltage scale between the forward biased (positive) direction and the reverse biased (negative) direction.]]
+=== Zener diode as a shunt regulator===
-A '''Zener diode''' is a type of [[diode]] that permits [[electric current|current]] in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the [[breakdown voltage]] known as  "Zener knee voltage" or "Zener voltage".
+[[Image:Zener reg.gif|left|frame|Simple Zener voltage regulator]]
+The Zener diode may be used as simple [[Linear regulator | shunt regulator]].  With an appropriate series connected current limiting resistor (R1), the circuit will provide an accurate voltage level independent of changes in either the input power supply (V<sub>S</sub>) or changes in the load (R2).
+This type of circuit is highly inefficient <ref> ARRL handbook (2006) page 5.19</ref>.  For a given (V<sub>S</sub>) the current is always constant since the Zener diode and load effectively form a current divider i.e., the circuit consumes power even when the load is disconnected{{reference needed}}.  This attribute must be considered when selecting a Zener diode to guard against possible destruction when the load is disconnected.
-A conventional solid-state [[diode]] will not allow significant current if it is [[reverse-biased]] below its reverse breakdown voltage.  When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to [[avalanche breakdown]].  Unless this current is limited by external circuitry, the diode will be permanently damaged.  In case of large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance.  The amount of the voltage drop depends on the semiconductor material and the doping concentrations.
+The [[resistor]] R1 supplies the Zener current I<sub>Z</sub> as well as the load current I<sub>R2</sub> (R2 is the load). R1 can be calculated as -
-A '''Zener diode''' exhibits almost the same properties, except the device is specially designed so as to have a greatly reduced breakdown voltage, the so-called '''Zener voltage'''.  A Zener diode contains a heavily [[Doping (semiconductor)|doped]] [[p-n junction]] allowing [[electron]]s to [[Quantum tunneling|tunnel]] from the valence band of the p-type material to the conduction band of the n-type material.  In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states; as a result of the reduced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on both sides. A reverse-biased Zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the Zener diode at the Zener voltage.  For example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of 3.2 V if reverse bias voltage applied across it is more than its Zener voltage. However, the current is not unlimited, so the Zener diode is typically used to generate a reference voltage for an [[amplifier]] stage, or as a voltage stabilizer for low-current applications.
+<math>R1 = \frac{V_{S} - V_{Z}}{I_{Z} + I_{R2}}</math> where, V<sub>Z</sub> is the zener voltage, and I<sub>R2</sub> is the required load current.{{reference needed}}
-The breakdown voltage can be controlled quite accurately in the doping process.  While tolerances within 0.05% are available, the most widely used tolerances are 5% and 10%.
-Another mechanism that produces a similar effect is the avalanche effect as in the [[avalanche diode]].  The two types of diode are in fact constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the [[Zener effect]] is the predominant effect and shows a marked negative [[temperature coefficient]].  Above 5.6 volts, the [[Avalanche breakdown|avalanche effect]] becomes predominant and exhibits a positive temperature coefficient.
+===Zener diode as a voltage reference ===
-In a 5.6 V diode, the two effects occur together and their temperature coefficients neatly cancel each other out, thus the 5.6 V diode is the component of choice in temperature-critical applications.
+[[Image:Ideal feedback model.svg|thumb|left| - almost the right schematic - The Zener diode may be used as the voltage reference to a regulated power supply]]
+* Make distinction between shunt regulation and VR - the Zener may be low power as the external pass element handles the current
-Modern manufacturing techniques have produced devices with voltages lower than 5.6 V with negligible temperature coefficients, but as higher voltage devices are encountered, the temperature coefficient rises dramatically.  A 75 V diode has 10 times the coefficient of a 12 V diode.
+Regulated power supplies often contain a Zener Diode as a voltage reference.  The output of the power supply ([[feedback]]) is compared to the  voltage reference in a comparator stage.  The comparator then adjusts the output of the power supply to maintain the feedback at the same level as the voltage reference thereby providing regulation.{{citation needed}}
-All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of "Zener diode".
+<s>
-Doping (semiconductor)
+These devices are also encountered, typically in series with a base-emitter junction, in transistor stages where selective choice of a device centered around the avalanche/Zener point can be used to introduce compensating temperature co-efficient balancing of the  transistor [[PN junction]]. An example of this kind of use would be a DC [[error amplifier]] used in a [[stabilized power supply]] circuit feedback loop system.
+</s>
+{{-}}
+===Zener diode as a clamp ===
+[[Image:Wiki.png|left|250px|thumb|Zener diode clamp used to limit the signal to an amplifier]]
+The voltage to a to a sensitive amplifier stage may be [[Clamp (circuit)| limited]] by using a Zener diode as shown in the accompanying figure.
+{{-}}
+===Zener diode as a noise generator ===
+[[Image:Wiki.png|left|250px|thumb|A white noise generator may be formed using a zener diode and a low noise amplifier]]
+A Zener diode may be used as a wideband [[white noise]] generator. <ref> Maxim Application Note 3469 (March 14, 2005) '''Building a Low-Cost White-Noise Generator'''.</ref>  This white noise is caused when a Zener diode operates in the reverse breakdown mode.  A low noise amplifier may be required to boost the signal to a usable level.
+{{-}}
+===Zener diode as a level shifter ===
+[[Image:Wiki.png|left|250px|thumb|The AC signal is level shifted...]]
-==Usage==
+An AC signal may passed through a Zener diode.
-=== Zener diode as a shunt regulator===
+{{-}}
-{{Unreferenced|date=December 2006}}
+==Specification==
-[[Image:Zener 3D and ckt.png|right|100px|thumb|Zener diode shown with typical packages. ''Reverse'' current <math>-i_Z</math> is shown.]]
+The specification for an individual Zener diode are available in the device's [[data sheet]].  While each data sheet contains many unique specification, this article will focus on breakdown voltage, power, and the temperature coefficient.
-Zener diodes are widely used to regulate the voltage across a circuit.  When connected in parallel with a variable voltage source so that it is reverse biased, a Zener diode conducts when the voltage reaches the diode's reverse breakdown voltage.  From that point it keeps the voltage at that value.
+===Breakdown voltage===
-[[Image:Zener diode voltage regulator.svg|220px|center]]
+* Voltages available (~1 - 100V)
+*Doping (semiconductor)
+===Power dissipation===
-In the circuit shown, resistor R provides the voltage drop between U<sub>IN</sub> and U<sub>OUT</sub>. The value of ''R'' must satisfy two conditions:
+* power (~0.25 to 50 W)
-# ''R'' must be small enough that the current through D keeps D in reverse breakdown. The value of this current is given in the data sheet for D. For example, the common BZX79C5V6<ref>[http://www.fairchildsemi.com/pf/BZ/BZX79C5V6.html ''BZX79C5V6 data sheet'', Fairchild Semiconductor]</ref> device, a 5.6 V 0.5 W Zener diode, has a recommended reverse current of 5 mA. If insufficient current exists through D, then U<sub>OUT</sub> will be unregulated, and less than the nominal breakdown voltage (this differs to [[voltage regulator tube]]s where the output voltage will be higher than nominal and could rise as high as U<sub>IN</sub>). When calculating ''R'', allowance must be made for any current through the external load, not shown in this diagram, connected across U<sub>OUT</sub>.
+The power dissipated by a Zener diode is a product of the voltage drop and amount of current passing through the Zener diode.  Consequently, the power rating is largely determined by case style (physical size and the [[heatsink]]).  A stud mounted device such as the XXXX may dissipate XXX watts while attached to a the specified minimum heatsink {{needs ref}}. The smaller 2N4735A may only disipate XXX watts{{needs ref}}.
-# ''R'' must be large enough that the current through D does not destroy the device.  If the current through D is ''I''<sub>D</sub>, its breakdown voltage ''V''<sub>B</sub> and its maximum power dissipation ''P''<sub>MAX</sub>, then <math>I_D V_B < P_{MAX}</math>.
+The maximum power dissipation is also dependent on the temperature of the device.  The Zener diode data sheet will normally present a chart [[derating]] the device.
-A Zener diode used in this way is known as a ''shunt voltage regulator'' (''[[Shunt (electrical)|shunt]]'', in this context, meaning connected in parallel, and ''[[voltage regulator]]'' being a class of circuit that produces a stable voltage across any load). In a sense, a portion of the current through the resistor is shunted through the Zener diode, and the rest is through the load. Thus the voltage that the load sees is controlled by causing some fraction of the current from the power source to bypass it&mdash;hence the name, by analogy with locomotive switching points.
+===Temperature coefficient===
-These devices are also encountered, typically in series with a base-emitter junction, in transistor stages where selective choice of a device centered around the avalanche/Zener point can be used to introduce compensating temperature co-efficient balancing of the  transistor [[PN junction]]. An example of this kind of use would be a DC [[error amplifier]] used in a [[stabilized power supply]] circuit feedback loop system.
+*Not applicable to all data sheets
+*sweet spot at ~6.2VDC
+== Lead identification ==
-Because it is almost always the ''reverse''-breakdown property of the Zener diode that is useful, in circuit schematics the Zener diode symbol (i.e., a diode arrow) typically points in the ''opposite'' direction of the circuit's positive current flow. This use is opposite that of a typical diode, which would be aligned with the current flow.
+[[Image:Zener 3D and ckt.png|right|100px|thumb|Zener diode shown with typical packages. ''Reverse'' current <math>-i_Z</math> is shown.]]
+The Zener diode is a two terminal device consisting of a cathode and anode.  The cathode is normally identified by a small band on the body of the device.  Larger devices may have the [[schematic symbol]] of the Zener diode printed on the case.  Refer to the manufactures [[data sheet]] if there are no identifiable markings.
-===Zener diode as a clamp ===
+== Theory of operation==
-The voltage to a to a sensitive amplifier stage may be [[Clamp (circuit)| limited]] by using a zener diode as shown in the accompanying figure.
+<s>
-===Zener diode as a voltage reference ===
+Because it is almost always the ''reverse''-breakdown property of the Zener diode that is useful, in circuit schematics the Zener diode symbol (i.e., a diode arrow) typically points in the ''opposite'' direction of the circuit's positive current flow. This use is opposite that of a typical diode, which would be aligned with the current flow.
-{{Expand section|date=March 2009}}
+[[Image:V-a characteristic Zener diode.svg|thumb|250px|Current-voltage characteristic of a Zener diode with a breakdown voltage of 17 volt. Notice the change of voltage scale between the forward biased (positive) direction and the reverse biased (negative) direction.]]
-===Zener diode as a noise generator ===
-{{Expand section|date=March 2009}}
+A '''Zener diode''' is a type of [[diode]] that permits [[electric current|current]] in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the [[breakdown voltage]] known as  "Zener knee voltage" or "Zener voltage".
-===Zener diode as a level shifter ===
-{{Expand section|date=March 2009}}
+A conventional solid-state [[diode]] will not allow significant current if it is [[reverse-biased]] below its reverse breakdown voltage.  When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to [[avalanche breakdown]].  Unless this current is limited by external circuitry, the diode will be permanently damaged.  In case of large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance.  The amount of the voltage drop depends on the semiconductor material and the doping concentrations.
-An AC signal may passed through a zener diode.  This allows a the bias a   be transfered thr
+A '''Zener diode''' exhibits almost the same properties, except the device is specially designed so as to have a greatly reduced breakdown voltage, the so-called '''Zener voltage'''.  A Zener diode contains a heavily [[Doping (semiconductor)|doped]] [[p-n junction]] allowing [[electron]]s to [[Quantum tunneling|tunnel]] from the valence band of the p-type material to the conduction band of the n-type material.  In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states; as a result of the reduced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on both sides. A reverse-biased Zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the Zener diode at the Zener voltage.  For example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of 3.2 V if reverse bias voltage applied across it is more than its Zener voltage. However, the current is not unlimited, so the Zener diode is typically used to generate a reference voltage for an [[amplifier]] stage, or as a voltage stabilizer for low-current applications.
-==Specification==
-{{Expand section|date=March 2009}}
+The breakdown voltage can be controlled quite accurately in the doping process.  While tolerances within 0.05% are available, the most widely used tolerances are 5% and 10%.
+Another mechanism that produces a similar effect is the avalanche effect as in the [[avalanche diode]].  The two types of diode are in fact constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the [[Zener effect]] is the predominant effect and shows a marked negative [[temperature coefficient]].  Above 5.6 volts, the [[Avalanche breakdown|avalanche effect]] becomes predominant and exhibits a positive temperature coefficient.
-===Breakdown voltage===
+In a 5.6 V diode, the two effects occur together and their temperature coefficients neatly cancel each other out, thus the 5.6 V diode is the component of choice in temperature-critical applications.
+Modern manufacturing techniques have produced devices with voltages lower than 5.6 V with negligible temperature coefficients, but as higher voltage devices are encountered, the temperature coefficient rises dramatically.  A 75 V diode has 10 times the coefficient of a 12 V diode.
-===Power dissipation===
- Zener diode achieved regulation by
-dependent on the case design.  A stud mounted device such as a TO XXX can dissipate over XX watts while a small surface mount device built into a SO-223 enclosure may only dissipate XX watts.
+All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of "Zener diode".
+</s>
 ==See also==
 * [[b:Zener diode|Wikibooks:Zener diodes]]