Rz in Zener Diodes: Modeling & Equivalent Circuit

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Discussion Overview

The discussion revolves around the concept of Rz in Zener diodes, focusing on its modeling and equivalent circuit representation. Participants explore the implications of Rz in both theoretical and practical contexts related to Zener diode functionality.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the definition and modeling of Rz in Zener diodes.
  • Another participant suggests that Rz may refer to the resistance of the diode itself, noting that real components exhibit resistance unlike ideal models.
  • A question is raised regarding the units of Rz, with a participant mentioning that R could also denote the temperature coefficient.
  • It is proposed that Rz might refer to a separate resistor used in conjunction with the Zener diode, which forms a voltage divider.
  • One participant states that Rz is the internal resistance of the Zener, typically around 22 ohms for silicon Zeners, and suggests modeling it as a series resistor with the diode.
  • A participant notes that for fast circuits, the Zener's resistance alone may not provide sufficient information due to additional real and capacitive components.

Areas of Agreement / Disagreement

Participants express differing views on the definition and implications of Rz, with no consensus reached on its exact meaning or modeling approach.

Contextual Notes

There are assumptions about the context in which Rz is applied, and the discussion does not resolve the complexities of Zener diode behavior in various circuit conditions.

EvLer
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In Zener diodes, what is Rz?
Could someone give me an idea how it is modeled, i.e. an equivalent circuit?

Thanks.
 
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Rz

Given no contex, I am just guessing, but I think it is the resistance of the diode. All real components have a certain amount of resistance as opposed to ideal models with no resistance. It is modeled simply by a series resistance.

Interestingly, batteries can be modeled as a variable resistor in series with a ideal voltage source. As the battery loses charge, the value of the resistance goes up until it consumes all the voltage from the battery. At that point the battery is "dead".
 
What unit does Rz have? Resistance?

Sometimes the letter R is also used for the temperature coefficient.

- Warren
 
Zener diodes are almost never used without a _separate_ resistor in series with them (okay, the two form a Voltage divider, and the "load" is taken across the zener. the Resistor is there to drop the unwanted, unregulated part of the voltage). My guess is that R_z refers to this _other_ resistor.

If the diode is to be used in fast circuits, the "resistance" of the zener would be insufficient info, as it will have Real and capacitative parts.
 
Rz is the internal resistance of the Zener.
While it depends on the material this is usually about 22 ohms for the average silicon zener.
To model it just put a resistor of Rz in series with the diode.
When you need to know how much power the zener will dissipate you need to know Rz.
 
How zener diode works?
 

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