1) Stable voltage Uz

The stable voltage is the working voltage of the Zener diode in the reverse breakdown zone, and the voltage value at both ends of the tube. This value changes slightly with the difference of operating current and temperature. Even for the same type of Zener diode, the stable voltage value has a certain degree of dispersion. For example, the stable voltage of 2CW14 silicon Zener diode is 6~7.5V.

2) Temperature coefficient

The change of temperature will change VZ. In the Zener tube, when |VZ|>7V, Vz has a positive temperature coefficient, and the reverse breakdown is an avalanche breakdown. When |Vz|<4V, VZ has a negative temperature coefficient, and the reverse breakdown is Zener breakdown. When 4V<|Vz|<7V, the voltage regulator tube can obtain a temperature coefficient close to zero. Such a Zener diode can be used as a standard Zener tube

3) Stable current Iz

Minimum stable current Izmin, large stable current Izmax stable current: the reverse current when the working voltage is equal to the stable voltage; minimum stable current: the minimum reverse current required when the Zener diode works at a stable voltage; the maximum stable current: Zener diode The maximum reverse current allowed to pass.

The concept of dynamic resistance rz is the same as that of general diodes, except that the dynamic resistance of Zener diodes is obtained from its reverse characteristics. The smaller the rz, the steeper the breakdown characteristic of the voltage regulator tube is reflected. rz=△Vz/△Iz4)

power dissipation Pz

When the reverse current passes through the PN junction of the Zener diode, a certain amount of power loss will occur, and the temperature of the PN junction will also increase. Determine the power dissipation of the tube according to the allowable PN junction operating temperature. Usually a small power tube is about several hundred milliwatts to several watts. Maximum power dissipation Pzm: The maximum power loss of the regulator tube depends on the area of ​​the PN junction and heat dissipation conditions. When working in the reverse direction, the power loss of the PN junction is: Pz=Vz*Iz, and Izmax can be determined by Pzm and Vz.

Zener diodes have a wide range of uses and are used very much. It seems that the application is very simple, but if you don't pay attention, it can be easily damaged. The following are some considerations when choosing:

1. Multiple Zener diodes can be used in series, but due to the relatively large discreteness of diode parameters, parallel use is not allowed.

2. The zener diode pins must be soldered at a distance of 5mm or more from the shell, and it is best to use an electric soldering iron below 30W for soldering. If using a 40～75W electric soldering iron for soldering, the soldering time should not exceed 8～10s. Try to use solder wire with built-in solder instead of bulk solder and rosin.

3. In order to compensate the voltage temperature coefficient of the Zener diode, the Zener diode can be used in series with the silicon diode (including the silicon Zener diode). The string of forward diodes must not exceed three, and it can also be used with special temperature compensation. The tubes are used in series.

4. Temperature has a great influence on the characteristics of semiconductor devices. When the ambient temperature exceeds 50°C, the maximum power dissipation should be reduced by 1% for every 1°C increase in temperature.