What is a Zener Diode? How Does it Work? Where to Use? ( Zener Diode Tutorial)

Hi guys! In this lesson, I will explain the  working principle of the zener diode, which is used for voltage stabilization in electronic  circuits. Zener diode is a diode that keeps the voltage applied to its pins constant.

When zener  diodes are connected to the circuit in the right direction, it works like a normal silicon diode.  In other words, they start to flow current after 0. 7V.

But they are not used that way. They  are used in reverse connection to the circuit. When connected in reverse, they do not  flow current up to a certain voltage value.

This voltage is called break or zener voltage.  After the breaking voltage, they start to flow current and the voltage value on them remains  constant at the breaking voltage value. In fact, we can say that it is a diode that flows current  in both directions.

They do the job of a voltage  regulator. Their color is usually orange, with  a black stripe at the cathode tips. The symbol is like this.

Now let's look at some examples to better understand the working principle. The zener diode, which finds a variety of  applications in order to provide a constant reference voltage or for protection purposes,  appears in many electronic circuits. Therefore,  there are zener diodes in many circuits that  undertake the functions of voltage stabilization, signal clipping, electronic element protection. 

To better understand the working logic, I built a circuit where the resistor and two  zener diodes are connected in series. Here,  there are zener diodes 1N5231 with a zener voltage of 5. 1V and 1N4728 with a zener voltage of 3.

3V. When we connect a 9V source to this circuit and  measure the voltage falling on a zener diode with the help of a multimeter, we see the zener  voltage of that diode. If we make the source 12V, the measured voltage will still be 3.

3V. If  we measure the voltage across the two diodes, we see the total zener voltage. In the same way,  even if we make the source 12V, the voltage will still be constant 8.

4V. Zener diode is used in  this way to ensure that many circuit devices operate at a certain voltage. In this case,  the element used will only work at voltages exceeding the zener voltage.

Thus, they keep the  voltage to the load constant and protect the load from excess current. So what will the zener diode  protect against high current? There is only one thing that can be done in this regard, and that  is to connect a big series resistor of suitable value in front of the zener diode.

In this way,  the zener diode is protected against high current. Let's do one more example. Here you can see that  three zener diodes with breakdown voltages of 5, 3 and 10V are connected in reverse and in  series.

A normal silicon diode is also connected. If we measure from this point in the circuit, we  see the breaking voltage value of the zener diode, 10V. For example, if we take an output from here,  we get 8V output from the total breakdown voltage value of 5V+3V.

If we take the output  from here, we get 10. 7V from 10V+0. 7V.

Finally, if we take output from all  of them, we can get 18. 7V output value from the sum of 5V+3V+0. 7V+10V.

As you  can see, we can get the voltages we want thanks to the zener diodes. With this  logic, adjustable voltage sources are made. The current-voltage graph of the zener diode  is as here.

In the case of forward polarity, that is, when it is connected straight, it starts  to pass current after a voltage of about 0. 7V like a normal silicon diode. In the case of non-reverse  polarity, it starts to pass current after the breakdown voltage and starts to regulate.

When we connect the zener diodes in series, we can increase the regulation voltage. For  example, when we connect two zener diodes with a breaking voltage of 5V in series,  we can obtain a regulation voltage of 10V, and similarly, we can increase the power when we  connect zener diodes in parallel. For example, when we connect two 0.

5W zener diodes in parallel,  we can provide a constant voltage to a 1W load. Zener diodes are used not only as a regulation  process in direct current, but also in clipper circuits for clipping operations at the desired  value in alternating current. As in the examples here, the sine-shaped AC input voltage is  clipped at the output by means of zener diodes.

If zener diodes actually do the job  of voltage regulators, you may have a question why zener diodes are used. This is  mainly due to the lower price of zener diodes. Here you can see the zener diode and voltage  regulator sample price comparison that can do the same job.

For a single one, these  price differences may seem like very little. But in industrial applications where we need  to use a lot, this ratio becomes important. This is the basic structure and  working principle of the Zener diode.

I hope it was helpful and you liked it.  Hope to see you in the next lesson. Goodbye.