# A zener diode question

#### Atakan

Dec 18, 2016
11
Who can solve this question and where is zener diode's resistance ?

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Jun 10, 2015
2,661
I can.

Dec 18, 2016
11

#### AnalogKid

Jun 10, 2015
2,661
Since this is a homework problem, first you show us your work. Then we advise.

ak

#### Atakan

Dec 18, 2016
11
Since this is a homework problem, first you show us your work. Then we advise.

ak
i did 10-5.6 / 100 = 0.044 A = Iz and then 5.6/220+2.2k= 2.3mA=IL and then already vo=vz namely vo=5.6V is it true ?

#### duke37

Jan 9, 2011
5,364
Put some brackets in your equations to define what should be calculated first. Thus 10-5.6/100 should read (10-5.6)/100

44mA is NOT Iz
5.6/(220+2k2)=2.3mA correct

#### Atakan

Dec 18, 2016
11
Put some brackets in your equations to define what should be calculated first. Thus 10-5.6/100 should read (10-5.6)/100

44mA is NOT Iz
5.6/(220+2k2)=2.3mA correct
5.6/100= 56mA so that iz=56mA and then il=2.3mA
if i sketch 100ohm's next to ix , namely, ix=iz+iL =2.3mA+56mA= 58.3mA= ix ?????
A question, What is A ? a is 0 or other ?

#### duke37

Jan 9, 2011
5,364
56mA is the current through the 100Ω resistor. This goes two ways, some through the zener and some through the series resistors (2.3mA) so what is left to go through the zener?

#### Atakan

Dec 18, 2016
11
56mA is the current through the 100Ω resistor. This goes two ways, some through the zener and some through the series resistors (2.3mA) so what is left to go through the zener?
ix=İz+İL
ix= (10-5.6)/100=44mA
il= 5.6/(220+2200)= 2.3mA
ix-il=iz 44mA-2.3mA= 41.7mA=iz
is it true?
And then what is vo?
Why is there ampermeter? what is value of ampermeter?

#### duke37

Jan 9, 2011
5,364
The diagram shows Vo=Vz but does not show where the output would be connected.
The meter is to measure the current through the bypass as the resistor is changed.

#### Atakan

Dec 18, 2016
11
The diagram shows Vo=Vz but does not show where the output would be connected.
The meter is to measure the current through the bypass as the resistor is changed.
thank you for helping , by the way, is my response true? if you say it , i am pleasure.

#### duke37

Jan 9, 2011
5,364
All seems to be correct, congratulations.

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Trevor, I have to click a "LIke" somewhere in this thread but I'm not settled on which of your replies it will be. You did a great job of walking him through the problem without actually doing the work for him.
56mA is the current through the 100Ω resistor. This goes two ways, some through the zener and some through the series resistors (2.3mA) so what is left to go through the zener?
On second thought it's got to be this one because it ends with a "?". It's reminiscent of how shrinks are depicted when the patient asks ..."Doc, do you think that this has anything to do with my problem"? And the \$100.00/Hr shrink (who never offers and opinion) invariably replies with ... "What do you think"?

Atakan, fortunate for you that Duke's therapy is free!

Chris

#### Petkan

Feb 9, 2011
19
Who can solve this question and where is zener diode's resistance ?

Atakan:

Here is a simple approach:
1. First assume the voltage across the zener is always 5.6V.
2. Calculate the current through its ballast resistor on the left as I=(Vin-Vz)/R
3. Calculate the load current as Vz/(Rload) (assuming ideal A meter with zero resistance)

Last edited by a moderator:

#### duke37

Jan 9, 2011
5,364
The resistance of a zener diode is used to describe the change in voltage as the current is changed. Often this resistance is taken as zero.
Free?
I was hoping for some Turkish delight.

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