2N7002 Idss

Close, perhaps... Vishay, for example, gives Idss leakage current as 1uA maximum at 60V 25C, and 500uA at 125C.

I can give you a few general pointers. First, for most MOSFETs I've measured, the leakage current is proportional to Vds, which means it can be modeled as a resistance. Assume a resistance that drops with temperature. Ahem, until one approaches breakdown, of course.

To complicate matters, the maximum leakage current for a given type varies considerably from manufacturer to manufacturer, and from batch to batch. However, the datasheet maximum leakage specs are usually VERY conservative from real parts, by factors of 100 to 10000, etc. This also varies from manufacturer to manufacturer and batch to batch.

For most FETs, it's doubtful.

--
 Thanks,
    - Win
Reply to
Winfield Hill
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How do I determine the Idss current at elevated temperatures and different Vds voltages for a 2N7002? The data is given as 1.0uA at 25C and Vds=45V. We know leakage current doubles every 10C so at +125C, Idss =

1uA*2^((125-25)/10)= 1mA but how does Vds effect this leakage current? Will a SPICE model yield good results in this area?

thanks, Harry

Reply to
Harry Dellamano

Vgs VS log(Id) is a straight line; the slope depends on manufacturer and FET type (logic, power, etc). If one does not fix the SPICe model, it fails to follow that log relationship at low currents. The same could be said concerning temperature effects Look in this NG under subject "oscillation in high-voltage" for one of the fixes. The other fix is to remove a (usually) 1meg resistor between the source and drain in the model. I have not checked these fixes over temperature.

Reply to
Robert Baer

Perhaps I should have made a different remark, re spice. Of course I believe you can make an accurate spice model of your circuit ideas.

I find that many, if not most, manufacturer and Spice-company-supplied models are sadly deficient. But with serious effort, you can create an appropriate model that matches your MOSFET in the respects that're important to you, and with additional attention to selected component parameters, you can create some impressively-accurate circuit models.

--
 Thanks,
    - Win
Reply to
Winfield Hill

Thanks Win, that is what I needed. Harry

Reply to
Harry Dellamano

I just tried a random 2N7000. 60 pA Idss at 9 volts.

Gate leakage looks very low. I can adjust the gate voltage for roughly

1 mA Id (9 volt battery and an LED) and then open the gate, and the Id is (visually) constant for some minutes so far.

John

Reply to
John Larkin

That's about 10x higher than my measurements.

Yes.

--
 Thanks,
    - Win
Reply to
Winfield Hill

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