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Looking for zener diode model.

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It is easy to model from the datasheet but in some areas only the worst case values, An engineer likes to think about what tolerance error needs to be.

This is roughly a 5% tolerance part at 5 mA @ 25'C but might be different tolerances with different parameters.
You could choose a 1% replacement or consider that 10% is acceptable. Yet you have not indicated the purpose.

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This is a slightly different spec +4%/-8% @ 5mA yet fairly close to the 1N4109 tolerance specs.

There are 3 voltage specs above that tells you about the ΔV/ΔI= R[Ω] for resistance or Z [Ω] for (incremental) impedance with different subscripts like ;

- ZK for impedance at Knee current (1 mA) 110 Ω max vs 100 Ω.
- R for Reverse leakage current VR = 11V @ [0.1 uA max] ( recall Zeners are forward conducting diodes in reverse)
- ZT for Threshold (5mA) The rated current and lowest Zzt= 30 Ω max.
 
Zener's are useful for limiting Vgs and often included in FETs at no cost penalty which will add some small amount of pF to the gate. But this is essential to protect it.

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In this case "any" 15V Zener may work for you.
Your choice of FET depends on speed and heat rise from RdsOn, yet there is very little difference from driving the gate to that RdsOn resistance with +/-5% tolerance or even +4%/-8% on Zener voltage. It is almost irrelevant.


If you are breadboarding, learn how NOT to create ESD damaging voltages with handling as you could easily damage the part before the zener was added.
 
Tony Stewart, yes that's exactly what I am doing with two zener's. Frequency? How do I determine the frequency of a mosfet? The on and off times?
 
Frequency of a square wave is approximated by the risetime for the harmonic at half power or -3dB. f=0.35/Tr for 10 to 90% risetime.
 
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