What is Zener Diode? Zener diodes are frequently used in electronic designs. They are generally used as voltage reference. Zener diodes work like a normal diode in case of correct polarization. However, when reverse polarization is applied, it transmits the voltage applied to it up to a certain voltage and breaks above a certain value. So they keep the voltage constant at that value. However, they convert the excess voltage on them into heat and throw it out. Therefore, although they provide a stable voltage, they cannot provide high current.
The voltage value at which zener diodes break is shown as Vz, known as the zener voltage or reserve voltage.
We have already mentioned that zener diodes convert voltages above Vz into heat. The amount of heat is related to the voltage that must be dissipated and the current passing through them. Therefore, there is a value of current that zener diodes can provide and this value is known as Izm.
Zener diodes are frequently used as voltage references. Therefore, it is important that the voltage level is stable. The ability of Zener diodes to remain stable in temperature changes is important. This value must be strictly observed in their use.
How to Measure a Zener Diode?
When measuring the zener diode; whether the zener diode is working or not and the breakdown voltage can be learned with the connection in the figure. A 9 volt zener is connected to the circuit below. In zener diode applications, the applied voltage is not required to be 9 volts. However, a voltage greater than the breakdown voltage of the zener diode is not applied. A value of resistance can be selected so that a current between 5-20 milli amperes (mA) passes through the zener. When a voltage of 12 volts is applied, a current flows through the zener diode. The passing current creates a voltage drop of 3 volts across resistor R. While 3 volts of the 12 volt supply voltage falls on the resistor, 9 volts are at the zener diode terminals.
Zener Diode Robustness Check
Diode integrity test with an avometer;
Zener Diode Robustness Check
When checking the integrity of the Zener diode, straight polarization is made in the buzzer stage of the avometer as in the normal diode to test whether it is intact.
First, the avometer is switched to diode mode.
The probes of the avometer are brought into contact with the two legs of the diode.
Then the probes are contacted to the legs of the diode in the opposite way.
If a large value is read in both cases or a small value is read in both cases, the diode is defective.
If a large value is read in one case and a small value in the other, the diode is good.