# Zener diode

1. Aug 31, 2006

### EvLer

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

Thanks.

2. Aug 31, 2006

### interested_learner

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".

3. Aug 31, 2006

### chroot

Staff Emeritus
What unit does Rz have? Resistance?

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

- Warren

4. Sep 1, 2006

### lightgrav

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.

5. Sep 2, 2006

### NoTime

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.

6. Sep 13, 2006

### aveenabeauty

How zener diode works?