As a rule, BJT output characteristics are presented as a family of particular characteristics representing the function of the collector current IC of the collector-emitter voltage VCE while the base current IB is kept constant as a parameter. Maybe this two-dimensional way of presentation is widely used since it is convenient for printing on paper...
When we automatically measure and plot BJT output characteristics by a computer (even the primary Apple II), we have the unique chance to present them in a more attractive three-dimensional way. Now the collector current is a function of two variables - the collector-emitter voltage and the base current; IC = f(VCE, IB). The image on the screen is a surface, in which the particular characteristics IC = f(VCE) are represented by separate vertical sections of this surface.
I implemented this attractive experiment in the early 90's when I was trying to make vocational teachers in Bulgarian carry out real computer experiments in the semiconductor laboratory... but they proved unprepared for this... A program written on MLBASIC (an assembler extension of the embedded interpretator) was controlling an Apple computer equipped with an analog periphery - 4 DACs, 4 ADCs, power voltage-to-current and current-to-voltage converters (described, regretfully only in Bulgarian, in the attached link after the pictures below).
It is amazing that then I had no idea that I will reproduce this attractive experiment with my students whole 25 years later... and really I will start doing it today... I made a "dress rehearsal" of the "show" at the university on Saturday evening. It was too late and dark in the laboratory... so movies I made were very poor (there was a mistake in the camera settings)...
https://drive.google.com/open?id=0B45uRPpHPD9hb3JabVh1alRFcmM
(Measuring of a 3-dimensional transistor output characteristic by MICROLAB)
https://drive.google.com/open?id=0B45uRPpHPD9hMWdzZW5MQzJxTTg
(Plotting a 3-dimensional transistor output characteristic on the screen)
https://drive.google.com/open?id=0B45uRPpHPD9hY3dyY1JLc0dvQ0k
(Temperature influence)
This question is closely related to the questions below:
https://www.researchgate.net/post/Why_do_we_use_Ib_instead_Vbe_as_a_parameter_when_measuring_common-emitter_output_characteristics
https://www.researchgate.net/post/How_do_students_investigate_semiconductor_devices_in_the_lab-manually_or_automatically
https://www.researchgate.net/post/How_do_we_investigate_semiconductor_devices_in_the_educational_lab
https://www.researchgate.net/post/How_do_we_investigate_the_IV_curve_of_a_forward_biased_diode-by_a_current_voltage_or_real_source
It would be interesting for me to see what you think about this way of presentation. Is it the actual output transistor characteristic or only another attractive presentation?
https://drive.google.com/open?id=0B45uRPpHPD9hcm5rOEEyaGlrMzA
Dear Cyril,
Any representation has its objectives.
Let us analyse the two figures representing the same data. That is the transistor curves.
The transistor i-v characteristics can be expressed formally by the function:
IC= f( VCE , IB)
From the two port notation of the transistor, the output port parameters are IC and VCE.
IB represents the effect of the input port current on the collector current.
Accordingly, to represent the output transistor characteristics on a two dimensional graph one has to choose VCE as a continuous variable and IB as a discrete variable having with proper steps. It is so that we sample the base current. This is the conventional way where the value of the base current is written on it as a label for the figure. Such transistor iv representation is used to solve graphically the tranistor circuit. We all know the concept of the load line and the DC operating point. so this presentation is characterized by its simplicity and ease of use.
Now it is to be compared by the three dimensional representation of the same transistor curves that you propose.
It is so that you add a third axes to represent the base current and then you have to draw the transistor curve at the new base current in an other plane shifted by the magnitude of the base current. So, there is no need to label the curve. This is the single benefit from the three dimensional representation. Which means that you use a different page to draw an i-v curve.
This new representation will complicate the concept of the graphical solution.
So, the only benefit is not to label the i-v curves with the base current but with a more complicated solution.
I do not see any advantage from the three dimensional representation of the the output tranistor curves. In the opposite it brings unneeded complications.
This is my opinion on your proposal.
Best regard
Cyril, my opinion is your way of presentation is very good. the output curves are these way( I versus two voltages) because eventually we can say that the transistor is a voltage-controlled current source.
Spectacular view - but unfortunately of low usage potential.
The output characteristics of a transistor are supposed to be used for simple, rough approximation of working point of a transistor. In order to do so from your 3D graph - one need to present it in orthogonal view without perspective - to be able to read out values at the axes. In such view though, one cannot easily distinguish different voltages , as they overlap (due to lack of perspective). n order to enhance visibility one may add a thicker contour at certain voltages to give eye a guideline - then viola! We end up in classic representation with few curves on XY chart.
This only applies for "engineering" or "quantitative" use of graph. Because your presentation allows way easier analysis of "qualitative" features of output characteristics.
Dear Cyril,
Any representation has its objectives.
Let us analyse the two figures representing the same data. That is the transistor curves.
The transistor i-v characteristics can be expressed formally by the function:
IC= f( VCE , IB)
From the two port notation of the transistor, the output port parameters are IC and VCE.
IB represents the effect of the input port current on the collector current.
Accordingly, to represent the output transistor characteristics on a two dimensional graph one has to choose VCE as a continuous variable and IB as a discrete variable having with proper steps. It is so that we sample the base current. This is the conventional way where the value of the base current is written on it as a label for the figure. Such transistor iv representation is used to solve graphically the tranistor circuit. We all know the concept of the load line and the DC operating point. so this presentation is characterized by its simplicity and ease of use.
Now it is to be compared by the three dimensional representation of the same transistor curves that you propose.
It is so that you add a third axes to represent the base current and then you have to draw the transistor curve at the new base current in an other plane shifted by the magnitude of the base current. So, there is no need to label the curve. This is the single benefit from the three dimensional representation. Which means that you use a different page to draw an i-v curve.
This new representation will complicate the concept of the graphical solution.
So, the only benefit is not to label the i-v curves with the base current but with a more complicated solution.
I do not see any advantage from the three dimensional representation of the the output tranistor curves. In the opposite it brings unneeded complications.
This is my opinion on your proposal.
Best regard
One may make the 3-D representation of the I-V transistor characteristics more informative by displaying on it the forward tranfer characteristics of the transistor IC= F( IB, VCE) where VCE is changed in steps and IB changed continuously. Hence, the the 3-d space will be more useful. This is my proposal to extend the idea of Cyril.
Best wishes
Dear Vasile,
I am happy that you responded to my answer on Cyril question. The transistors are characterized by manufacturer data sheets for their applications. The data sheets contains the static IV characteristic, the small signal equivalent circuit parameters for amplifier applications and the switching parameters in case of switching applications.
If the descriptions in the data sheets are not sufficient, one can follow the experimental approach led by you and by Cyril.
In addition there are laboratory equipment produced for characterizing the transistor such as the semiconductor parameter analyzer and the network analyzer.
From the circuit point of view, the circuit is designed to make it less sensitive on the transistor parameters .
I hope that i understood which you aim to.
Bet wishes
Maybe I really had to clarify the objectives of this experiment...
I am a teacher of this basic subject and my main task is first to show and explain the behavior of semiconductor devices (transistors) - how the voltages across and currents through the input base-emitter and output collector-emitter sections are related... and only then to show how to use these relationships for calculation...
So the purpose of this experiment is to assist in solving the first task. This is an attractive demonstration that only complements, not replaces, the next in-depth study of the device...
Indeed, yesterday I used it exactly this way - I started the program at the beginning of the laboratory exercise, and made it measure and draw a number of output characteristics over a long time interval, during which students were assembling their experimental settings with oscilloscopes...
The interesting thing, however, was that THEIR OWN creations (simple circuits with several elements mounted on solderless) were much more meaningful and important to them than my computerized experiment significant only for me (since it was MY OWN creature:)
Dear cyril
Yes. I understand the objectiveness of your question and gave a direct answer on it.
You search for the best demonstration of the tranistor output characteristics. Therefore you proposed you three dimensional representations.
You relay on that you have one dependent parametric, which is IC and two independent parameters CE and IB. Is that okay.
Best regardss
By the way, do you see the hyperbole representing the maximum allowable power dissipation?
Pmax = 0.25 W and Imax = 100 mA are set in the beginning of the program. When any of the two limits is reached, the processing of the current characteristic is suspended and the program begins processing the next.
Quote: "BJT output characteristics are presented as a family of particular characteristics representing the function of the collector current IC of the collector-emitter voltage VCE while the base current IB is kept constant as a parameter."
I only want to point to the fact, that there is another family of curves with constant VBE as a parameter. It is true that in many cases IB=const is used because of practical reasons and because the slope of these curves gives us the EARLY voltage. However, a set of curves with IB=const does not imply that the current IC would be controlled by IB.
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