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[SOLVED] zener diode output voltage doesn't exceed, then where does the rest of the voltage go?

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RAHUL_KUMAR

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zener diode output voltage dont exceed, then where the rest voltage goes?

How does the zener diode work to give almost constant output voltage parallel across load, even if the input supply voltage is increased.
My question is where does the extra voltage goes ??
if input is 12v ,and zener is 10 let say, then where the 2v goes? ( if we don't limit the current by using external resistor , and providing the limited current in mA by the source itself).
 

Re: zener diode output voltage dont exceed, then where the rest voltage goes?

You miss the point: a Zener will not work unless the current to it is limited, that's why you almost always see a resistor in series with them. If not a resistor, there will be some other method of limiting the current. The voltage is dropped across that resistor or current source.

Example:
12V ---- resistor ---- 10V Zener ---- 0V
2V is dropped across the resistor and 10V is dropped across the Zener diode.

If you connect 12V directly across a 10V Zener diode it will be destroyed.

Brian.
 
Re: zener diode output voltage dont exceed, then where the rest voltage goes?

A diode (led, zener) automatically adjusts its internal resistance, so that a certain voltage develops across its leads. By presenting the right amount of resistance, it conducts the right amount of current according to Ohm's law (which is a simple equation), so as to produce the right voltage according to the diode equation (which is complicated).
 

Re: zener diode output voltage dont exceed, then where the rest voltage goes?

You miss the point: a Zener will not work unless the current to it is limited, that's why you almost always see a resistor in series with them. If not a resistor, there will be some other method of limiting the current. The voltage is dropped across that resistor or current source.

Example:
12V ---- resistor ---- 10V Zener ---- 0V
2V is dropped across the resistor and 10V is dropped across the Zener diode.

If you connect 12V directly across a 10V Zener diode it will be destroyed.

Brian.

sir, resistor is used to limit the current , (to protect the zener from getting damaged) but if the source itself is providing 12v with some mA current then why should be the resistor be used?

please rectify me, if i am saying anything wrong what i understood, you are saying that resistor is used for two purpose , 1st to limit the current and 2nd that zener will not work as a voltage reference if resistor is not used.
 

Re: zener diode output voltage dont exceed, then where the rest voltage goes?

Hi,

You don't understand.
Betwixt clearly said: "unless the current to it is limited, "

--> If you have a current limited power supply, then the power supply haas some internal resistance. This doesn't need to be a real resistor but a circuit that regulates the current (limit).

And as soon as the current limiter becomes active --> there is no 12V at the output anymore.
But you said "constant 12V" which is not true for a current limited power supply.

[12V ---- resistor] ---- 10V Zener ---- 0V
So your power supply (brackets) includes the resistor.

Klaus
 
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