The flow of electrons is always from anode to cathode outside of the cell or device, regardless of the cell or device type and operating mode, with the exception of diodes, where electrode naming always assumes current in the forward direction ( that of the arrow symbol ), i. e., electrons flow in the opposite direction, even when the diode reverse-conducts either by accident ( breakdown of a normal diode ) or by design ( breakdown of a Zener diode, photo-current of a photodiode or solar cell ).

The terms anode and cathode should not be applied to a Zener diode, since it allows flow in either direction, depending on the polarity of the applied potential ( i. e. voltage ).

An exception is when a diode reverse-conducts, either by accident ( breakdown of a normal diode ) or by design ( breakdown of a Zener diode, photo-current of a photodiode or solar cell ).

Like a typical diode, there is a fixed anode and cathode in a Zener diode, but it will conduct current in the reverse direction ( electrons from anode to cathode ) if its breakdown voltage or " Zener voltage " is exceeded.

The difference between the avalanche diode ( which has a reverse breakdown above about 6. 2 V ) and the Zener is that the channel length of the former exceeds the mean free path of the electrons, so there are collisions between them on the way out.

: These are actually a JFET with the gate shorted to the source, and function like a two-terminal current-limiter analog to the Zener diode, which is limiting voltage.

| Zener diode symbol

| Zener diode

This effect, called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference.

The Zener diode is named for Dr. Clarence Melvin Zener of Carnegie Mellon University, inventor of the device.

* BZ-series silicon Zener diodes ( e. g.: BZY88C4V7 4. 7V Zener diode )

The green outlined section ( based on Q16 ) is a voltage level shifter named rubber diode, transistor Zener or V < sub > BE </ sub > multiplier.

* Zener diode

Zener diode

Zener diode shown with typical packages.

A thyristor is used in conjunction with a Zener diode attached to its gate, and when the output voltage of the supply rises above the Zener voltage, the thyristor will conduct, then short-circuit the power supply output to ground ( and in general blowing an upstream fuse ).

The field-induced promotion of electrons from the valence to conduction band of semiconductors ( the Zener effect ) can also be regarded as a form of FE.

In some electronic devices, electron transfer from one material to another, or ( in the case of sloping bands ) from one band to another (" Zener tunneling "), takes place by a field-induced tunneling process that can be regarded as a form of Fowler-Nordheim tunneling.

In this configuration, the output levels can be modified by appropriate choice of Zener diode, and these levels are resistant to power supply fluctuations ( i. e., they increase the PSRR of the comparator ).

If properly constructed, tests of this nature can circumvent the issues of bias and cheating common to standard Zener card tests.

A TVS diode is a type of Zener diode, also called an avalanche diode or silicon avalanche diode ( SAD ), which can limit voltage spikes.

Temperature dependence can be compensated using the circuit of Figure 6 that includes a standard diode D ( of the same semiconductor material as the transistor ) in series with the Zener diode as shown in the image on the left.

Grain growth can be inhibited by second phase particles via Zener pinning.

Laboratory-grade Zener diode secondary solid-state voltage standards used in metrology can be constructed with a drift of about 1 part per million per year.

Buried Zener references can provide even lower noise levels, but require higher operating voltages which are not available in many battery-operated devices.

Zener can refer to:

Note that the output voltage will always be about 0. 65V less than the Zener due to the transistor's V < sub > BE </ sub > drop.

On the other hand, in the previous case, the output voltage was depending on the power supply, while now it is defined by the Zener diodes ( which could also be replaced with a single double-anode Zener diode ).

Although Zener cards are usually used to test for clairvoyance, they may also be used to test for telepathy, in which case one subject will draw a card and attempt to mentally project the image on it to the mind of another subject.

Thus, as long as the Zener current ( I < sub > Z </ sub >) is above a certain level ( called holding current ), the voltage across the Zener diode ( V < sub > Z </ sub >) will be constant.

In some DC circuits, a varistor or two inverse-series Zener diodes ( collectively called a transorb ) may be used instead of the simple diode.

Name of the race may be related to Zener Cards which are used to conduct test for clairvoyance and telephatic abilities.

More refined black boxes placed a diode in parallel with the resistor to provide a larger DC pulse to activate the F relay than if only a resistor was used, or replaced the resistor with a 36 V Zener diode which regulated the voltage drop across the telephone to a level where the D relay would not activate, regardless of the length of the local loop.

These are electrically very similar to Zener diodes, and are often mistakenly called Zener diodes, but break down by a different mechanism, the avalanche effect.

The pioneering work in this field was done by Stueckelberg, Landau, and Zener in the 1930s, in their work on what is now known as the Landau – Zener transition.

It is a shunt regulator and operates by way of the Zener diode's action of maintaining a constant voltage across itself when the current through it is sufficient to take it into the Zener breakdown region.

Here, the load current I < sub > R2 </ sub > is supplied by the transistor whose base is now connected to the Zener diode.

The circuit is readily made adjustable by adding a pot across the Zener, moving the transistor base connection from the top of the Zener to the pot wiper.

Finally it is occasionally made microadjustable by adding a low value pot in series with the Zener ; this allows a little voltage adjustment, but degrades regulation.

This led to the development of a set of cards known as Zener cards, invented by Karl Zener.

In Star Wars Episode I: The Phantom Menace ( 1999 ), ( as a reference to Zener cards ) a young Anakin Skywalker, in an interview with the Jedi Council, had to perceive ( in a clairvoyance-like test ) a device that projected images on a monitor held by Yoda, in order to examine the power and control of Anakin's Force-wielding abilities.

These findings were later exploited by Bell Labs in the development of the Zener diode, which was duly named after him.

Pro Electron naming for transistors and Zener diodes has been widely taken up by semiconductor manufactures around the world.

Once the electric field intensity increases beyond a critical level, the p – n junction depletion zone breaks down and current begins to flow, usually by either the Zener or the avalanche breakdown processes.

In this bipolar junction transistor ( BJT ) implementation ( figure 4 ) of the general idea above, a Zener voltage stabilizer ( R1 and DZ1 ) drives an emitter follower ( Q1 ) loaded by a constant emitter resistor ( R2 ) sensing the load current.