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-   -   2 Zeners versus 1 zener- inconsistent with actual theory?! (http://www.physicsforums.com/showthread.php?t=470376)

 wushumaster Feb6-11 03:04 PM

2 Zeners versus 1 zener- inconsistent with actual theory?!

So when I have two zeners connected, I should get less voltage than if I had one, but this is NOT the case!!! Why?
I don't understand- two zeners of say 1000 V each- say we have a power source than provides 2500 volts- then we should get only 500 V. With one of these zeners, we should get 1500 V. But it's almost reversed, and I don't get why..
Thanks!!!

 Fish4Fun Feb6-11 07:28 PM

Re: 2 Zeners versus 1 zener- inconsistent with actual theory?!

wushumaster,

You should probably include some details like how the zeners are connected. Next you should explain why on earth you are attempting to use zeners with a 2500V supply. You should probably include some details about your supply voltage, at the very least confirm that it is a DC supply.

Fish

 berkeman Feb7-11 11:28 AM

Re: 2 Zeners versus 1 zener- inconsistent with actual theory?!

Quote:
 Quote by wushumaster (Post 3123603) So when I have two zeners connected, I should get less voltage than if I had one, but this is NOT the case!!! Why? I don't understand- two zeners of say 1000 V each- say we have a power source than provides 2500 volts- then we should get only 500 V. With one of these zeners, we should get 1500 V. But it's almost reversed, and I don't get why.. Thanks!!!
When you connect two zeners in series, the overall voltage drop is the sum of the two zener voltages.

When you connect two equal-value zener diodes in parallel and drive them with a current source, the voltage drop is slightly less than when you have just the one zener diode. That is because the two parallel zener diodes are splitting the available current, so each diode voltage is a little less since it's running at a lower current.

http://en.wikipedia.org/wiki/Zener_diode

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