linear_guy
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Posts posted by linear_guy
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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?
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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?
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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!
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Hi Attila, can you pls look into this? The Tracer Vrc and Vrb boxes are backwards.
Thanks.
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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?
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Do I need to uninstall first before installing new version?
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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).
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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?
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Maybe Sho can give us a part number. The IRF150 is enhancement mode NCH FET, not depletion mode. Vgs needs to be -3V or more negative for drain current to go to zero.
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Thanks. Didn't think to look there.
Is the source impedance of the wavegen's 50 ohms? Do you publish the schematic for the AD2? A simplified one?
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I've looked thru the online documentation and found a screenshot showing a 'burst' capability. See attached.
But my Waveforms 3.19.5 doesn't show the Trigger, Wait, Run, Repeat options in the Simple mode. Is there a hidden set of options?
Effect of activating option Ib/Vbe when using transistor tester with WaveForms Tracer
in Test and Measurement
Posted
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. 😃