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I have a question!.

As I understand,the 3 diodes are "more or less" the same but with really important differences:

  • Zener diode: Clamps voltage at a breakout lvl.
  • Schottky diode: Like Zener but it lose less voltage in forward mode and it switches way faster.
  • TVS-Diode: The transient voltage supressor is to improve between other applications the EMC (Characteristics against EMV noise).

Am I right? The point of this question, is that as to test, I took a Schottky diode, where the Breakout Voltage was 40V. I connected it directly to battery. As i tested that with 24 V, a low current value was flowing (obviously). But I expected that as any resistance was connected in between, it would burn out more or less when it triggers (ideally at 40V).

The source did not have a current consumption bigger than 40 - 50 mA. After 40V, it should be like a 0 Ohm resistor, right? It worked like that until a value of 56V, where it directly exploded. How is that possible?

Thank you very much!. Greetings.

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Manuel,

Zener and TVS diodes are similar in that they are normally operated with reverse bias voltage. Zeners are mostly operated at breakdown to act as a voltage regulator or clamp. TVS diodes are used for protection against spikes from ESD and other transient events. They normally operate below breakdown where they have little effect on the circuit they are protecting. Schottky diodes are much different in that they do not operate above the breakdown voltage and are used primarily as rectifiers. They also have a significantly lower voltage when they are forward biased. Exceeding the breakdown voltage can damage them as you found out.

Hope this helps

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  • \$\begingroup\$ Thank you very much!. I did not know that Schottky weren´t supposed to work only Forward. I have also a question then. I have a TVS Diode wich Vbr is 6V, which produces 1mA. It is supposed to protect from ESD events 16kV directly contact and 30kV by air. Why is then the Vbr so low? \$\endgroup\$ – Manuel Joaquín Jul 26 '18 at 16:56
  • \$\begingroup\$ Vbr is the voltage at which the TVS begins to conduct, so you don't want to use it in a circuit that has voltages above that. When the TVS is subjected to ESD the voltage that it will clamp to is much higher than Vbr. \$\endgroup\$ – EE_socal Jul 26 '18 at 18:46
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No, your understanding is not correct. Zener diodes are designed to have a specified reverse bias breakdown, and these diodes are typically used in reverse bias. A Schottky diode is specified to have a minimum reverse bias breakdown voltage but the actual breakdown may occur at a much higher voltage. The attractive feature of a Schottky diode is its low forward voltage.

When operating any diode in reverse bias you must be careful to limit the current to avoid destroying the diode.

Saying that a diode in reverse breakdown is like a "0 ohm resistor" is a very simplified notion of how it behaves.

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  • \$\begingroup\$ Thank you very much! I didnt know that the Schottky were not precise in the break voltage event. I think that answer a lot of questions! \$\endgroup\$ – Manuel Joaquín Jul 26 '18 at 16:57

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