Zener voltage reference

[hayowazzup]

Hi,

Could anyone tell me if zener diode has a relatively poor regulation comparing to normal diode? For voltage referencing, how does normal diode work better than zener? or am I wrong?

 

[yadavvlsi]

There are two types of breakdown mechanism in diode.

1. Avalanche breakdown : This kind of breakdown occur in lightly dopped diodes. Carriers are accelerated with high electric field. These accelerated carriers colloid with atoms in semiconductor lattice and break covalent bonds. Again the accelerated carriers colloids with lattice generating more carriers. As a result of collision a large amount of heat is generated. If normal diode is used in reverse bias. It will burn off soon.

2. Zener breakdown: Zener breakdown occurs in heavily dopped diodes. Heavily dopped diode have very small depletion region. Due to small depletion region high electric field generated which breaks the covalent bonds and generates a large number of carriers. In this case, Carriers are generated by breaking covalent bonds due to high electric field not by collision. So less heat is generated.

Zener diode is heavily dopped diode. So Zener breakdown mechanism is dominating in Zener diodes. Break down mechanism in normal diode is avalanche. Zener diode is used as a voltage regulator while normal diode is used for rectification.

 

[andre_luis]

hayowazzup

The beneficits of Zenner diode is the ability of concuct higher electrical reverse current than standard diodes.
However, if the bias currend is polarized much under nominal scpecified value, the zenner voltage DECREASES !

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[hayowazzup]

does the zeners tolerate much higher temperature over normal diodes?

 

[andre_luis]

You need research at datasheets. There are devices optimized to operate at extended temperatures.

But, keep in mind that to the purpose of standard diodes ( foward polarized ), drift voltage over temperature don´t matter.
The same tolerance cannot be applied to zenner diodes wich are purposed to work reverse polarized.

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[yadavvlsi]

Zener diodes can handle more reverse bias current than normal diode without generating large heat.

 

[andre_luis]

Hi,

Could anyone tell me if zener diode has a relatively poor regulation comparing to normal diode? For voltage referencing, how does normal diode work better than zener? or am I wrong?

Maybe this answe your question :

**broken link removed**

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[sowmia04]

can u explain operation of tunnel diode with its energy band structure plz

 

[umesh49]

You may find a zener diode with good tolerance like 1%, but still the zener diode tolerance will be more for whole operating temperature. It would always diffcult to achieve really good performance due to variatio in non linear region of characterstics. It is always recommened to use normal diode in series if you needs a good voltage regulation.

 

[Orson Cart]

It is a classically known solution that a 4v7 zener in series with a 1N4148 gives a stable reference (driven from a simple current source) over a modest temp range (0-40 degC) as the negative TempCo of the diode offsets almost exactly the pos TempCo of the 4v7 zener. Regards, Orson Cart.

 

[sherazi]

a normal diode doesn't regulate! it rectifies only ! conducts when forward biased else doesn't conduct! and if reverse breakdown occurs thats avalanche breakdown...

a zener is meant for regulation ! and works in zener breakdown ...

 

[hayowazzup]

You may find a zener diode with good tolerance like 1%, but still the zener diode tolerance will be more for whole operating temperature. It would always diffcult to achieve really good performance due to variatio in non linear region of characterstics. It is always recommened to use normal diode in series if you needs a good voltage regulation.

So normal diodes in series has a better regulation than a single zener in reverse biased? Could you please tell me if there's any books or websites that tells about it?

---------- Post added at 11:44 ---------- Previous post was at 11:34 ----------

It is a classically known solution that a 4v7 zener in series with a 1N4148 gives a stable reference (driven from a simple current source) over a modest temp range (0-40 degC) as the negative TempCo of the diode offsets almost exactly the pos TempCo of the 4v7 zener.

is it the circuit in Figure 5?
Current source - Wikipedia, the free encyclopedia

Is it only for zener above 5.6v? Could you please explain how the TempCo matching of the diodes work? I thought the purpose of the diode is to compensate the change in temperature of transistor. So I guess it is better to have , the TempCo of transistor + tempCo of the normal diode = -TempCo of Zener , for a better temp tolerance? I realised TempCo for zener is in mV/K whereas for normal diodes its in mv/C, they are the same, right?

 

[Orson Cart]

a normal diode doesn't regulate! it rectifies only ! conducts when forward biased else doesn't conduct! and if reverse breakdown occurs thats avalanche breakdown...

a zener is meant for regulation ! and works in zener breakdown ...

It looks as though you may not have fully understood the post, Regards, Orson Cart.

 

[Syncopator]

a normal diode doesn't regulate! it rectifies only ! ...

Not really.

It can also clamp (limit) and is the simplest mixer, e.g. a.m. detector.

 

[sherazi]

ya it can clamp!....