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creating PNP caracteristicsby sweeping plot in LTspice from a circuit I built

 

Hello , in the attacehd zipped file I have created a basic PNP biasing circuit . The simultion is in time domain , I added plots of different ports.
Is a there a way by clever type of sweep to recreate the basic characteristics plot of the attached PNP plot?
Current vs Vce plot.
Thanks.
/g/LTspice/files/Temp/03_01_25.zip
 

On Mon, Mar 31, 2025 at 07:27 AM, john23 wrote:
Is a there a way by clever type of sweep to recreate the basic characteristics plot of the attached PNP plot?
Sweep the collector voltage.
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Sweep the base current over a number of steps.
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Do not do this as a .TRAN simulation.
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In your circuit, remove R1, R2, and R3.? Replace V1 with a current source.
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Use one .DC command that specifies two sources.? If I remember correctly, the "1st Source" should be the collector voltage, and the "2nd Source" should be the base current.? Sweep the collector voltage with fine increments (0.1 V or smaller), and sweep the base current over a smaller number of steps (0.2 uA increments).
?
Andy
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Sorry, I also should have said this:? Ground the Emitter and connect the negative collector voltage source to the transistor's collector.
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Obviously, the graph you uploaded needs to be inverted (or plotted with negative voltages going right and negative currents going up) when using a PNP.
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Andy
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Hello,I would like to try and implement the caracteristics with the circuit I made (attached)
By sweeping V1 (emitter source I see 0 current increases after Vbe>0.7)
Hopwever I cant see if the PNP is in saturation or linear states.
PNP have current structure where we can see by the current slope that PNP is saturated or linear.
How can we create such current plot?
Thanks.?
?
/g/LTspice/files/Temp/Draft2%20%281%29.zip
 

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Your message is confused, your.ASC is unsuitable. Looking at currents will not tell you about saturation, which is when Vce drops to a very low value, like 0.4 V or less. It never does that in your .ASC.

On 2025-04-01 19:20, john23 via groups.io wrote:
Hello,I would like to try and implement the caracteristics with the circuit I made (attached)
By sweeping V1 (emitter source I see 0 current increases after Vbe>0.7)
Hopwever I cant see if the PNP is in saturation or linear states.
PNP have current structure where we can see by the current slope that PNP is saturated or linear.
How can we create such current plot?
Thanks.?
?
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On Tue, Apr 1, 2025 at 02:20 PM, john23 wrote:
Hello,I would like to try and implement the caracteristics with the circuit I made (attached)
Do you wish to sweep the curves of this one unique circuit?? Or do you wish to sweep the curves of a PNP transistor?
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If you want to plot curves of this one unique circuit, then first you need to know what are the curves that you want to sweep.? What properties of this one circuit do you want to see in a plot?
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PNP have current structure where we can see by the current slope that PNP is saturated or linear.
How can we create such current plot?
See my circuits in "PNP_sweep.zip" in the Temp folder.? They plot the Ic/Ib and Ic/Vbe curves for just the PNP transistor.? The Ic/Ib plot is the one you most often see, because the transfer from Vbe to Ic is strongly nonlinear.? The Ic/Ib plot is also the one that corresponds to your photo "2.png" that you uploaded yesterday inside your "31_03_25.zip".
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Andy
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Hello Andy,I have taken your circuit and changed the current source into voltage source ,also Imade the voltage potential the same way put the voltage source in the collector.
I got a very close plot to what you got but the slope of the active mode is much higher.
Why is my slope shown in the attached photo much higher with respect to what you done?
Thanks.
 

On Wed, Apr 2, 2025 at 07:59 AM, john23 wrote:
Hello Andy,I have taken your circuit and changed the current source into voltage source ,also Imade the voltage potential the same way put the voltage source in the collector.
Why do you want to modify the circuit?
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What is the purpose of adding resistors, and changing the base drive from a stepped current source to a voltage that also depends on Vce?
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I think you need to answer these questions before thinking about the results with your circuit.? For what purpose are you doing this?? Are you doing it just to ask annoying questions, or do you have an actual goal in mind?? Without that, your questions seem meaningless and without purpose.
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I got a very close plot to what you got but the slope of the active mode is much higher.
Why is my slope shown in the attached photo much higher with respect to what you done?
Look at your circuit, and what you have done to it.
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You added resistance to the transistor.? Resistance changes the slopes.
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You applied the base drive between the base and ground, while simultaneously sweeping the emitter voltage.? Therefore, as the emitter voltage increases, the base-emitter voltage also increases (negatively), turning ON the transistor much much harder.? By the time V1 reaches 5 V, the base-emitter voltage in your circuit exceeds -1.6 V which means the transistor is being turned ON extremely hard.? The base current is unusually large for a small-signal transistor and it is fully saturated over most of the sweep range.
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Your circuit makes no sense to me.? Please explain the function of your circuit.? Did you plan it, or did you arbitrarily connect some components?? Please help me understand why you did this.
?
Andy
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This might help answer your question:
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Why is my slope shown in the attached photo much higher with respect to what you done?
The slope is greater because of V1 and R2.? ?As the voltage from V1 increases, Vc increases almost the same because the transistor is in saturation.? Ohm's law applied to R2 gives you the slope.
?
Andy
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On 02/04/2025 13:59, john23 via groups.io wrote:
Hello Andy,I have taken your circuit and changed the current source into voltage source ,also Imade the voltage potential the same way put the voltage source in the collector.
I got a very close plot to what you got but the slope of the active mode is much higher.
Why is my slope shown in the attached photo much higher with respect to what you done?
You circuit is completely messed up. If you wanted to reproduce Andy's plot, why didn't you use his circuit? To get the characteristic in a datasheet, you need to exactly use the conditions quoted in the datasheet. Don't introduce spurious resistors that are not in the test circuit that the manufacturers used.

Please check: PNP_OP_Chacteristic.zip

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Regards,
Tony

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