Hello, Genarally we use zener diode in reverved biased operation.
We need to make sure the current is within the spec in order to get
In my simulation ,The 1N750 get 1.4mA currect when its reversed biaed to 4.7V.
In the table below they say that maximal reversed currect is 5uA a thounthand times less then what is showing in the simulation.
So it means that my zenner diode will be burned?
Thanks.

 

hi yef,
Read this link.
https://quick-learn.in/what-is-zener-diode/
E

 

The given reverse current (5 to 50 µamps, in the table) are given for a specified reverse voltage (table: 1.5 volts).
This is the current for a voltage with a magnitude well BELOW the coresponding voltage Vz.
This is a kind of leakage current which (unfortunately ) does exist within the "off-region".

 

Yes , for 1.5V reversed bias voltage ,the zener diode current will be 5uA.
so I want the reversed bias voltage of 4.7V(I know there is some series resistor value also)
How can I know the current i need to supply this device so it will give me that 4.7V reveresed biased(with a small addition from series resistor).
Thanks.

 

hi yef,
This is with a 12V supply at a nominal 10mA Zener current.
What is your V supply and required zener current???
E

 

I am using the Zenner diode to reduce the VGS of the mosfets shown below.
before adding the zenner diode my Vgs was 12V which would burn the mosfet.
Now I have Vgs of 4.7V .
So my only corcern is for the zenner to function properly.Do you think it gets enogh current to have 4.7V reversed biased?
Thanks.

 

Hi yef,
Voltages required?
E

 

Hello Eric, I forgot to mention i added the simulation files.
In- =-12V

 

hi,
This plot shows the voltage across the Zener and its current, a 470R
E

 

Hello Eric, exactly , I have 1.8mA on D3.
Isnt it too little current?
Thanks.

https://www.mouser.co.il/datasheet/2/268/1N746A_1_1N759A_1_2c1N4370A_1_1N4372A_1-3442192.pdf

 

Hi,
This is without the Zener, So when the Zener is in circuit, it's clamping effectively as it should be.
E

 

Hello Eric, I am looking for datasheet basis that the 1.8mA current is enough for the D3 zener.
Thanks.

 

I am looking for datasheet basis that the 1.8mA current is enough for the D3 zener.

Hi yef,
Why???
It is a clamp, and it is clamping the Vgs at that low current as the design requires it to do.!!!

Simply put, it is working.
E

Updated:
This sim shows the Vclamp voltage, for a range of Zener currents. OK

 

Look at the left side of this curve. Anywhere between Iz(min) and Iz(max) will have the voltage near the Zener voltage.

 

Hello,What is the minimal current in the datasheet for this device?
Thanks.

https://www.mouser.co.il/datasheet/2/268/1N746A_1_1N759A_1_2c1N4370A_1_1N4372A_1-3442192.pdf

 

Take the numbers in that table for the max current and the leakage current to label the curve I posted above, than read Iz(min) from the graph.

Not particularly accurate, but I think you can deduce that it will be less than 1mA.

 

Do you think it gets enogh current to have 4.7V reversed biased?

Any reverse voltage will reverse-bias the Zener.
If the current is less than Izt then Its Vz will be less than 4.7V, which is okay for your application.

The test Izt for the rated Vz is 20mA (below):