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characteristic defect

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25mV ripple noise on your gate supply is probably the main problem you are seeing.  I like my gate voltage controlled to +-0.1mV.  


The other problem might be just the voltage reading accuracy as some of your voltage steps seem to go backwards.


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Message 21 of 27

What about the delay timing before measurements, how should I choise it please, I am really lost.

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Message 22 of 27

Hi again community 

I am still working on the characteristic of the transistor, I get like  weird plots, instead of the current increases with gate voltage ,it decreases. 

the first plot is the white one : Vg=0V.

the second is the red one : Vg=0.1V.

can you help to understand if is it a hardware problem or a software problem.

the VI that I am using is attached below .sample n3 test2 voltage to 8v.PNG


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Message 23 of 27

Looks more like you've fried that transistor and its now behaving like a resistor.  Try another transistor and see if it behave better.  If not and you get the same result, then look at your wiring.  Pay attention to grounding.  If you haven't changed the code its not software related.


Message 24 of 27

I put the transistor on a shielded box that I made , then I soldered the wires between the pins of the transistor and the NI Elvis breadboard.


Pay attention to grounding.

I am using the PSU (supply+ to the drain , ground to the source), and one output to the gate.Also one input to measure voltage (input+ to the drain, input- to the source) ,and DMM for current Id.


what if I reverse the measurements by starting with a high voltage on the gate ,then decrease it.

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Message 25 of 27

I don't understand what you soldered, but the heat from soldering can easily burn out a device.  Try a new one.


Hi to Lo or Lo to Hi should give you the same characteristics.  So sure try reversing the order to confirm whether the device is dead or alive.



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Message 26 of 27


today I tried a new transistor, but  still the resistance increasing  when the gate voltage increase .

white plot:VG=0V.

red plot:VG=0.01V.

green plot:VG=0.02V.

sample2 t2 test2 step0.01.PNG

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Message 27 of 27