Effect of activating option Ib/Vbe when using transistor tester with WaveForms Tracer

[hugocoolens]

What is the result/effect of activating the option Ib/Vbe when using the transistor tester module with WaveForms Tracer software?

Related to this: Is there a manual which describes the options and parameters which are selectable in the WaveForms Tracer software?

 

kind regards,

Hugo

 

 

Edited March 27, 2023 by hugocoolens
badly phrased question

[attila]

Hi @hugocoolens

The AD2/Adapter has two scope channels so it can measure 2 parameters at a time. With the "additional measurements" checked the other 2 parameters are measured automatically in sequence with another capture.

https://digilent.com/reference/_media/reference/test-and-measurement/transistor-tester-adapter/analog_discovery_transistor_adapter_sch.pdf

[linear_guy]

I think this is related to the thread.  When I hook up an NPN transistor w/o using the Digilent adapter, the Vrc and Vrb labels seem to be in the right location.  That is, the collector settings are in the top row and base settings in the bottom row.  But the settings boxes should be swapped.  The top settings control the base voltage with waveform1 and the bottom settings sweep the collector voltage with waveform 2.  Also I have to select "Ic/Vbe" to get the trace to look right, Ic/Vce doesnt work.

Does the Digilent adapter do some magic to get this right?

 

And do I need the adapter to get the hFE selections work?

[attila]

Hi @linear_guy

The sweep/step can be changed with the following buttons:

 

[linear_guy]

Thanks for the reply but I don't think you addressed my questions.  I'm not using the adapter.  And it's strange, my GUI showed the settings next to Vrc affect the base drive (in your image 0V to 4V) and settings next to Vrb affect collector voltage (in your image 700mV to 1.5V).  The boxes on top ought to be swapped with the bottom boxes.

Also, mouse scrolling is very wonky when I try to go up/down within these boxes.  For example, if -1V is selected and I scroll, the value jumps to -5V and then to -4.5V, but it doesn't allow lower values.  If I select the pulldown, I can select -2V or -1V again, but scrolling doesn't work.  I think the Tracer defaults to Auto mode, so that might be interfering.  I'm curve tracing a PNP.  EDIT: It doesn't matter whether NPN or PNP,  and It doesn't matter if it's running or stopped.  I noticed that when I pull down to see all the values, it jumps to the most negative value in the list.  EDIT: Never mind, I selected the wrong polarity (PNP vs NPN).

Edited December 14, 2023 by linear_guy

[attila]

Hi @linear_guy

The scroll will be corrected in the next version.
The problem was that when switching between PNP and NPN (without adapter, ground reference level), the order in the preset list was not changed, but the scroll took it as if it had been changed.

Fixed will be like this:

[attila]

Hi @linear_guy

 

[linear_guy]

Do I need to uninstall first before installing new version?

[attila]

There is no need to uninstall since it will upgrade sections which are needed.

[linear_guy]

OK thanks.  Operator error on the polarity and scrolling issue.

But again, I'm pretty sure the Vrc and Vrb boxes are reversed when I use No Adapter.  The Vrc boxes set the base voltage, and the Vrb boxes set the collector sweep amplitude.  Can you please look into this?

[linear_guy]

Hi Attila, can you pls look into this?  The Tracer Vrc and Vrb boxes are backwards.

Thanks.

[attila]

Hi @linear_guy

Sorry but I don't see the problem.

The top row starting with Vrc controls the W1 and the bottom row starting with Vrb controls the W2.

With 'No Adapter' the drawing on the left shows the circuit setup:

With Adapter the drawing it does not show the connections since these are controlled by relays on the adapter.

With Adapter the Emitter (setup GND) is referenced to +/-5V (V+ or V-) to have 10V range.
Without Adapter is by default referenced to AD GND but this can be changed under Options.
The signals are generated the same way and measurements performed the same way.
For devices with 2 oscilloscope channels and Adapter additional measurements are performed automatically in a second run, like above the Ib/Vbe checkbox.

For devices with 4 oscilloscope channel it expects a different setup:

As you can see the 'Ic/Vce(Ib)' uses Rb and 'Ic/Vce(Vbe)' expect no (short on) Rb:

[linear_guy]

On 1/22/2024 at 4:13 AM, attila said:

Hi @linear_guy

Sorry but I don't see the problem.

The top row starting with Vrc controls the W1 and the bottom row starting with Vrb controls the W2.

With 'No Adapter' the drawing on the left shows the circuit setup:

 

As you can see the 'Ic/Vce(Ib)' uses Rb and 'Ic/Vce(Vbe)' expect no (short on) Rb:

 

Hi Attila,

I found the problem was that I followed the Instructables drawing and they swapped W1 and W2.  Once I reversed the connections, the boxes now make sense. 

One thing that could be improved in the GUI is the 'Auto' button.  It's really hard to tell whether it's active or not.  Is there a way you could make it more obvious?  For example, use a bright background color when enabled, and a muted/gray when Auto is turned off.

"With 'No Adapter' the drawing on the left shows the circuit setup:"  Do you mean the circuit on the *right* side?

When I run in Ic/Vce(Ib) mode, the value in the Rb box has no effect on the collector current.  I can set it 10k, 100k, 1k, 100 -- no difference in the plot.  I was expecting that the GUI would calculate a base current from the Vbe applied.  And the curve trace plot (collector current) is the same whether I use  Ic/Vce(Ib) or Ic/Vce(Vbe).  If the latter mode expects zero ohm Rb, then Ic should be very non-linear.  Collector current ought to go very high when Vbe is above 700mV.  What am I doing wrong? 

Also the checkbox next to the transistor type doesn't let me check/uncheck it.  The ref manual says it selects 'Ib/Vbe'.  Has the feature been removed?

I am running version 3.21.19.

Thanks!
 

[attila]

Hi @linear_guy

The checkbox for secondary measurements is available with Adapter. This will perform two measurements toggling the relays of the adapter.
With 4 channel scope (line ADP3450) all the measurements are performed at once.

[linear_guy]

Hi, can you address the problem I'm having with the Rb base resistor setting?  Waveforms doesn't do anything with the setting, whether it is 100k, 10k, 1k, etc.  I'm expecting the collector current to increase if I change Rb to a lower value.  What gives?

[attila]

Hi @linear_guy

Have you actually changed the base resistor ?

Here is R1 with 1k and Trace with 10k Rb

[linear_guy]

I'm not asking about whether the actual resistor makes a difference, I know that it does.  I use a fixed 10k resistor. 

I guess I'm answering my own question.  Waveforms doesn't calculate the base current, right?  (unless it does when you plot hFE)  It should be something like (Vrb-0.6)/Rb_setting.  But it doesn't display Irb, it displays Vrb.  Is the point in having an Rb setting only used for the Adapter case? 

 

 

[attila]

Hi @linear_guy

No, it does not calculate since that would be an assumption.
All voltage and currents are measured with 4 scope channel devices and with Analog Discovery Adapter. This uses two sweeps and relays to measure each parameter. AD without adapter can measure 2 parameters at a time.

[linear_guy]

If the Rb setting doesn't do anything, why doesn't the GUI gray it out or show a blank?  Otherwise the user has a false sense that the control has an impact.  Consider this an improvement. 😃

[attila]

Hi @linear_guy

It does if you measure Ib. The scope channel 1 differentially measures Ib = C1/Rb