# Zener diode

Discussion in 'Homework Help' started by JoyAm, Sep 10, 2014.

1. ### JoyAm Thread Starter Member

Aug 21, 2014
112
4
Hello,
There is a problem when i am asked to calculate the current that flows through a zener diode as well ass the voltage of the output. Also i am asked to check if the diode is indeed in the zener zone, i calculated the first two values but i dont know how to check if the diode is on zener

2. ### MrChips Moderator

Oct 2, 2009
14,509
4,271
At first, ignore the value of R2 and assume that the zener diode is not conducting.
Calculate the voltage across RL using standard voltage divider equation.
This will establish if the zener voltage has been exceeded.

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3. ### dalam Member

Aug 9, 2014
58
6
Zener diode is in breakdown region. Because if you consider that it is reverse biased and make it open circuit you will get a voltage of 10 around it. And it requires 5v to enter into saturation so it is in breakdown region.
Your values of Iz is correct.

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4. ### JoyAm Thread Starter Member

Aug 21, 2014
112
4
This way the voltage at RL is 10 volts so it has exceeded it by double. That means that the diode is indeed working on zener because it keeps the output voltage at around 5 volts when we assume it works this way ?

5. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,673
1,536
Are you calling V2 the zener diode?

On edit ... my mistake. I see it is Vz on the schematic.

Last edited: Sep 10, 2014
6. ### dalam Member

Aug 9, 2014
58
6
If you want to check if any diode is on or off consider all possible case and check which combination is satisfying the circuit. Only one should do it.

7. ### JoyAm Thread Starter Member

Aug 21, 2014
112
4
My handwriting is confusing you here i guess what you see as V2 and R2 were supposed to be Vz and Rz so yes this is the zener sir.

Yeah thats true but it will not tell me if its specific in zener, right ?

8. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,174
1,188
Exactly, and this is true, only if Zener diode is connected in property way.

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