I'm a beginner at electronics and I wanted to buy a 5.1V zener diode with a Pd of 500mW. I've noticed that the test current (Izt) of these diodes are either 50uA, 5mA, or 20mA. I have two questions:
1) What exactly is zener test current?
2) What's the significance of this and how would it affect an electronic circuit?
You can use the zener voltage, as a fixed reference voltage, which will remain reasonably stable with power supply voltages ranging from about 8 to 18 Volts in the 12 volts example.
Bear in mind not to exceed the zener power rating and try to keep the zener current within 5 - 15 mA range.
The voltage across a zener diode is not constant but depends on the current flowing in the diode.
This effect is especially noticable in those low voltage zeners of a few volts. For example, a 3.6V zener in my component box have a breakdown voltage of only 2.95V at less than 1mA current, 3.3V at ~3mA and 3.6V at about 5mA or more.
Therefore to specify a zener diode, the manufacturer will typically use a certain constant current to test them.
For an user, if you want the zener to give you a fairly stable and accurate voltage, you have to supply the zener with a stable current.
A zener diode that has a test voltage at a low current has a much higher voltage at a higher current.
A zener diode with a high test current might not regulate the voltage at a low current.
Hi all,
Do u know about zener ?? Zener has internal resistance and other action,so could u tell me all bout this,please?? I'm welling to know, who could answer to me? And i hope so,thanks!!
Hi all,
Do u know about zener ?? Zener has internal resistance and other action,so could u tell me all bout this,please?? I'm welling to know, who could answer to me? And i hope so,thanks!!