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characteristic defect

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hello

I am working on a VI to plot the characteristic of a MOSFET, and I don't know.where is.the problem, when I plot it ,the measured voltage doesn't  back to the zero as fast as the output voltage when it start from the zero.

so I got the characteristic that is attached bellow.

 

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No one here tries to debug a picture.

Attach your VI.

"If you weren't supposed to push it, it wouldn't be a button."
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Message 2 of 27
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hello

yes thank you for your advice.
I am working on a VI to plot the characteristic of a MOSFET, and I don't know.where is.the problem, when I plot it ,the measured voltage doesn't back to the zero as fast as the output voltage when it start from the zero.
so I got the characteristic that is attached bellow.

the VI is attached bellow too.

 

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Message 3 of 27
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We cannot know what speed you expect. Is there a theory?


LabVIEW Champion Do more with less code and in less time
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Message 4 of 27
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I don't know what you mean by "the measured voltage doesn't back to the zero as fast as the output voltage",
but I've noticed the following in your block diagram:

  1. Your wiring is very messy (You are more likely to get people to help if you present something clean)
  2. You appear to be using the same device name ("Dev3") to reference four different devices (make sure you are referencing the correct devices)
  3. Due to lack of data flow control, the order of execution of your express VIs is undefined.  (Wire the error terminals to enforce order of execution)
"If you weren't supposed to push it, it wouldn't be a button."
Message 5 of 27
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what I am expecting is just like any characteristic of a MOSFET. 

a picture of the MOSFET's characteristic in general is attached bellow .

a picture of what I got is attached too.

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Message 6 of 27
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Solution
Accepted by topic author vispacespace123
06-11-2019 03:30 AM

I test transistors for a living.  There are a whole bunch of potential problems you could be experiencing, but the simplest is to clean-up your code as suggested and then see if that helps. Here's a start...

tracer_caracteristique_CDS.png

 

Now, as what else could causing the 100mA offet at Vds=0V?  It might be due the lack of dataflow in your VI, you might have been measuring before it set Vds=0V.  Its unclear from your previous VI what order things would happen in.

 

Then there's the fact you are using Express VIs, which is hiding all the settings of your Elvis system.  All I see is you are setting a 2A limit (range?) on the DMM.  What is the resolution on that range?  What are the specs of PSU in terms of slew rate and settling time?   Maybe you need to allow a few seconds for the PSU and DMM to settle before measuring?

 

Remember what happens here.  You sweep Vds to the maximum, then immediately back to Vds=0V for next sweep.  It might be that the PSU has a capactior that takes a few seconds to discharge.  Add a delay at the end of the Vds sweep and see if things improve.

 

Then there's the part we don't see..your wiring and connections.  Breadboard connections aren't ideal.  That could be having an impact.  There's also the device itself.  Do you have a spec sheet and plot of the real device performance?  Have you damaged it with ESD?

 

Finally, you have about 5 posts, with different code and questions all over the forums now.  Don't do that.  Stick to one thread unless the topic changes.

 

Craig

Message 7 of 27
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OMG I got it finally!!
I really appreciate your explanation, I am still a beginner and I am Learning with you , thank you.

On my breadbord I am using only the MOSFET ,I noticed that is started to warm up after only 3 plots , so I need to add a resistor (1khoms) to the drain, should I change something in my VI? also  what should I expect from the plot?
a picture of my final plot is attached below.
the VI is attached too.

 

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Message 8 of 27
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Hi vi,

 

some modifications:

check.png

so I need to add a resistor (1khoms) to the drain, should I change something in my VI?

Why do you want to change your VI?

 

also what should I expect from the plot?

What's the purpose of all that MOSFET characterization?

Best regards,
GerdW
CLAD expired, using 2009SP1 + LV2011SP1 + LV2017 (+LV2018 sometimes) on Win7+cRIO
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Message 9 of 27
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hi 

thank you for the modification, I didn't find the 'rampby delta'labview 2015

What's the purpose of all that MOSFET characterization?

I want to add a resistor to the drain so I can change the voltage till 10V without burning my transistor. 

the purpose is to get the characteristic of the MOSFET BS170 with NI Elvis.

I add it but I didn't get the saturation and the measured voltage is stuck to zero.

here is the plot with resistor (1kohm)with 1kohms.PNG

 

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Message 10 of 27
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