Zener Diode Fundamentals (A Newbie’s Information)

On this information, you’ll be taught precisely how a Zener diode works and the way to use it in circuits.

Do you know that a number of the widespread issues you’ll be able to construct with Zener diodes embrace easy energy provides and guitar pedals?

Sounds fascinating? Let’s bounce in!

Zener Diode symbol

What Is a Zener Diode?

A Zener diode is a sort of diode that’s usually used for voltage regulators and shaping waveforms.

Its image is an arrow pointing in the direction of a crooked line. There are literally three other ways you’ll be able to draw the Zener diode image in schematics:

3 zener diode symbol alternatives
3 ways to attract the Zener Diode Image

Whereas a traditional diode solely permits present to stream by a circuit when it’s forward-biased (present going from anode to cathode), the Zener diode additionally works when it’s reverse-biased (present stepping into the wrong way).

With normal diodes, for those who place it in reverse, no present flows.

At the very least, so it seems. However truly, for those who apply sufficient voltage in reverse, present will begin to stream.

This voltage known as the breakdown voltage of the diode.

For instance, the rectifier diode 1N4001 has a breakdown voltage of 50V.

The Zener diode is mainly the identical as the usual PN junction diode. Nonetheless, it’s specifically designed to work in reverse bias with a low and specified reverse breakdown voltage.

Reverse-biased zener diode

So, why is that fascinating?

Since you’re not restricted to the usual ahead voltage of 0.7V. You possibly can design the breakdown voltage to be for instance 3.3V or 12V – or many different voltages. The producers name this Zener Voltage (Vz).

This implies a Zener diode can act as a voltage regulator as a result of it retains the breakdown voltage at an almost fixed worth throughout its terminals.

How To Make A Zener Diode Voltage Regulator

Making a voltage regulator is straightforward with the Zener: Simply add a resistor!

Zener diode voltage regulator circuit

Right here’s the way it works:

When a voltage (have to be larger than the Zener voltage) is utilized throughout the resistor and Zener diode, the diode begins conducting in reverse and retains the voltage drop throughout it at a continuing worth of three.3V.

The remainder of the voltage drops throughout the resistor. This implies the resistor acts as a current-limiting resistor in an effort to simply calculate the present through the use of Ohm’s regulation.

Voltage regulator

The resistor (RS) limits the utmost present that may stream by the circuit. If there isn’t a load related to the circuit all the present flows by the Zener diode, inflicting it to dissipate its most energy.

A smaller worth of resistor RS offers you a better most present. However on the similar time, you must just remember to don’t exceed the utmost energy ranking of the Zener. Due to this fact, it’s necessary to decide on the best worth of collection resistance.

Instance: Selecting a resistor for a 12V to three.3V voltage regulator

On this instance, you’re going to make use of a Zener diode that may deal with as much as 2W of energy. What’s an acceptable worth for the resistor (RS)?

Mathematical analysis of  regulating circuit

First, you should discover the utmost present that may stream by the Zener diode:


That signifies that the minimal worth of the resistor is:


So a price of 14.5 Ω is absolutely the minimal. However you should utilize larger resistances in fact.

Subsequent, you should verify how a lot present your load wants. The load resistor is 1 kΩ, so its present is calculated as follows:


That’s a lot decrease than the 0.6A you’d get from the 14.5 Ω resistor, so no drawback right here.

If you wish to use a better resistor worth, simply use the next system along with your chosen resistor worth and guarantee that it’s above the present you want in your load:

I_{z} = frac{V_{in}-V_{z}}{R_{S}}

For instance, if you wish to use a 100 Ω resistor, this could offer you a most present of:

I_{z} = frac{12V - 3.3V}{100 Omega}} = 0.087A

Nonetheless, excessive above the wanted 0.0033A for the load, so that you’re good to go.

That mentioned, Zener diodes have their disadvantages. Take a look at this text about why Zener diodes make awful voltage turbines.

Wave-Shaping With the Zener

Within the earlier instance, you noticed how the Zener works with DC energy. Nonetheless, what occurs when it’s used with AC energy? How wouldn’t it react to a continually altering sign corresponding to an audio sign?

Take a look at the next circuit:

Zener in AC

Within the above diagram, the Zener diode has a Vof 5V, so if the waveform exceeds this restrict, the diode will “clip off” the surplus voltage from the enter, leading to a waveform with a flat high sustaining a continuing output of 5V.

When forward-biased, the Zener diode behaves like a daily diode. So when the waveform reaches adverse values under 0.7V, the Zener acts like a typical rectifier diode, leading to output clipping at -0.7V.

Zener Diode Instance: Distortion Guitar Pedal

Diode clipping and clamping circuits can form a waveform to supply an output waveform with a unique form. A clipper circuit clips off the constructive or adverse a part of an AC sign, which is why they’re generally used as waveform shaping circuits.


Once you reduce off the highest of an audio sign, it sounds distorted. That is precisely what you need in a distortion guitar pedal!

However the output sign of an electrical guitar isn’t excessive sufficient to be clipped. So to be able to clip it, you have to amplify it first. Right here’s a fundamental guitar distortion pedal circuit that makes use of Zener diodes to distort the sound:

So, for those who construct the circuit above the output waveform might be clipped on the VZ voltage plus 0.7V, which is the ahead voltage drop of the opposite diode.

Zener Diode Traits (The I-V Graph)

Zener I-V behavior

The I-V traits curve of a Zener diode is proven within the picture above. By learning this graph, it turns into clear why Zener diodes are employed in reverse bias.

By observing the habits of a Zener diode, you’ll be able to discover that because the reverse voltage rises, the reverse present additionally will increase step by step till it hits the Zener knee present, IZ (min). At this level, the breakdown impact begins, and the Zener impedance (ZZ), which is the inner resistance of the diode, begins to quickly lower because the reverse present will increase.

On the whole, the breakdown voltage of the Zener (VZ) is pretty fixed, though it will increase barely with rising Zener present (IZ). VZ is usually set at a price of the Zener present generally known as the IZ (min).

A Zener diode’s capability to take care of virtually fixed voltage in its breakdown area makes it appropriate for regulating voltage even within the easiest voltage regulator functions.

A voltage regulator’s primary position is to ship a gentle output voltage to a load related in parallel. That is even when the availability voltage has ripples or the load present varies. Zener diodes can keep a continuing voltage output so long as their reverse breakdown area holding present doesn’t drop under IZ (min).

Widespread Zener Diode Voltages

Right here you’ve gotten a desk with the most typical Zener voltages in diodes of 0.3 W and 1.3 W.

0.3W BZX55 zener diode
2.4V 2.7V 3.0V 3.3V 3.6V 3.9V 4.3V 4.7V
5.1V 5.6V 6.2V 6.8V 7.5V 8.2V 9.1V 10V
11V 12V 13V 15V 16V 18V 20V 22V
24V 27V 30V 33V 36V 39V 43V 47V
1.3W BZX85 zener diode
.3V 3.6V 3.9V 4.3V 4.7V 5.1V 5.6 6.2V
6.8V 7.5V 8.2V 9.1V 10V 11V 12V 13V
15V 16V 18V 20V 22V 24V 27V 30V
33V 36V 39V 43V 47V 51V 56V 62V

Extra Diodes Tutorials


Leave a Reply

    Your Cart
    Your cart is emptyReturn to Shop