What is zener voltage when 40mA of current flows in zener?

[opampsmoker]

Hi,
What is zener voltage when 40mA of current flows in zener?.....the 9V1, SOD123 zener as follows....

https://www.diodes.com/assets/Datasheets/ds18004.pdf

Datasheet doesnt say

 

[betwixt]

Seems a silly question to ask. You choose the voltage, at 40mA it will be 9.1V +/- tolerance if used in reverse bias mode and about 0.7V in forward mode.

Brian.

 

[FvM]

The datasheet doesn't specify zener voltage at 40 mA. It can be nevertheless extrapolated from given information.

You are aware of device power rating and its preconditions? The intended operation point involves a large temperature rise, zener voltage t.c. must be taken into account.

 

[KlausST]

Hi,

I can't find the chart for 9V1.
But I see 9.1V @ 5mA
And Z = 15 Ohms.
So the additional current of 35mA may cause additional voltagevdrop of 35mA x 15 Ohms = 525mV.
Thus 9.1 + 0.53 = 9.63 V.
In reality I expect less.

Klaus

 

[Audioguru]

Why are you operating the 5mA zener diode at 40mA which heats it to a little higher than its maximum allowed temperature even if it has air conditioning?

 

[opampsmoker]

Thanks, the 40mA are just spikes, but i would like the zener to alwsys clamp below 11V...otherwise a MOSFET gate will be blown.

 

[d123]

Hi,

I can't find it now, been searching for some app note that I'm certain mentioned it. Zeners are messy/loose/lousy. I seem to recollect you can use e.g. a TL431 voltage reference as a Zener replacement for the MOSFET gate clamp which is supposedly more accurate than the Zener. Revision O (and presumably other versions) of the TL431 datasheet has a walk-through of using it as a comparator, I guess that is basically and in a relative way how it is used as a Zener for MOSFET gates, but don't take my word for it as I haven't thought about the link between both circuits much.

 

[Audioguru]

The little 9.1V/5mA zener diode will clamp occasional 11V/40mA spikes fine.

 

[crutschow]

you can use e.g. a TL431 voltage reference as a Zener replacement for the MOSFET gate clamp

Not necessarily.
The TL431 is likely not be fast enough to clamp a spike, which is what the OP wants.
It's also overkill, as the Zener should work fine for his requirements.