BJT's don't work like that

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Thread Starter

Ratch

Joined Mar 20, 2007
1,070
comesoftware,

You also shredded my comment to multiple quotes (you shredded it "physically" but you have not won the argument), not to mention beenthere's comment as well (but I can only talk for me), almost taking it out of context and making it more difficult to respond to.
I separated it, but I did not change the wording, did I? I do that so that I can reply to every point you make in the paragraph. I know it gets difficult to keep track of the previous points and counterpoints made. Do you have a suggestion? Ratch
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
Dave,

The e-book introduction states the authors intention very clearly:
Intention is not the same as an explanation of associative relation.

The underlying physics is clearly tied to the subject of BJT and its importance is exemplified by the very fact that it is outlined in the second paragraph of the whole BJT chapter. The reader is rightly not fed with information that is covered (more appropriately) elsewhere in the e-book, and they are encouraged to read up on the relevant material should they so feel it is necessary.
I have no problem with the quoted paragraph from the e-book. But how does the e-book and your comment above relate to whether transistors are voltage or current controlled?

Interesting you should note Sedra and Smith's equation for the collector current as a function of Vbe; Ebers-Moll, an accurate empirically derived representation of the behaviour of the PN junction. The important parameter is one you have skimmed over, and that is the saturation current; in fact the saturation current, or Is as I'll refer to it from hereon-in, is a parameter that is both a function of the transistor physicality's (namely the width, length, and areas of the transistor geometry), doping concentrations, carrier diffusivity, and operational conditions (most importantly the temperature). Variability in any of these parameters will result in variability in Is, therefore even for constant Vbe, Ic is a function of the above factors. (Put this into context, Is will approximately double for increases of 5C in temperature - and consider the impact on the collector current for constant Vbe when the temperature rises by say 10C).
Yes, I am familiar with Is and what it can do.

Therein we have an interesting observation:

- In the first instance we have a voltage controlling parameter, Vbe, and a controlled parameter, Ic, related by a parameter (Is) that is a function of a multitude of extenuating variables.

- In the second instance we have a current controlling parameter, Ib, and a controlled parameter, Ic, related by a parameter (B) that is a function of a multitude of the same extenuating variables.

Therefore interestingly we have an equivalence of two models that describes a voltage-controlled device and a current-controlled device.
Yes, Is and all the things that influence it affect the collector current. So does Vt. But no one tries to send a signal into a transistor thermally, or by changing the size of the silicon slivers, or changing the doping. They do it by changing the BIG variable that really can be changed dramatically, Vbe. Whether they do it by setting the base current, or any other means, the Vbe will determine what the collector current will be.

Therein we can see that Sedra and Smith conclude that the BJT can be modelled as both a voltage-controlled and current-controlled device. This should come as no surprise by virtue of the fact that Vbe and Ib are inseparably connected, one cannot exist without the other. Furthermore, the transistor does not function without either parameters; without Vbe the b-e junction is not forward biased and there is no emitter current, without Ib there is no replenishment of the majority carrier in the base following recombination.
Coexistence does not mean dual control. If you can increase the collector current by changing the base current without changing the Vbe, then you have dual control. Otherwise the base current in a BJT is just a nuisance waste current proportional to the collector current.


Practitioners, such as Horowitz and Hill of Harvard University, utilise the current-controlled model as it provides the simplest method for designing real circuits that work...
Yes, that is true. Design is simplified when advantage is taken of the proportionality of the collector current to the base current. I have no problem with that. I have a problem with the explanation of how a transistor works. What I have not seen proven is that a transistor is a current controlled device. So far, all I have seen are current manipulation methods which ensure a correct Vbe is applied.

Given the e-book here at AAC commences its treatise of BJTs in the same vein as that in Art of Electronics by focusing on the practicing elements of the devices:


Quote:
Originally Posted by All About Circuits
My intent here is to focus as exclusively as possible on the practical function and application of bipolar transistors

I commend the current-controlled model of the transistor detailed in this e-book as both accurate and appropriate.
Accurate for designing circuits, but not accurate to say that a transistor is a current controlled device. Ratch
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
beenthere,

As ever, sophistry loves to talk. Where is that convincing demonstration to support these otherwise empty assertions? Absolutely nothing you have said supports your case in any concrete way. It takes experimental results to do that. Haven't seen anything but ASCII on paper yet.....
The case has been presented. All the raw data from experiments have been done many times in many places. The assertions have been made by Beaty, Alyward, and myself. Now it is up to you to disprove any of the points made to prove the central thesis of "Transistors are voltage controlled devices."
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
beenthere,

Quote by Ratch
Not easily, after all this is a web driven forum, not a physical laboratory in a college classroom.


Answer by beenthere
How conveniently inconvenient. So no method can be described? We just take your word for it?
You know I am right about a physical laboratory. Beside all my points reference equations and principles that have been plowed over and over again. You should examine my reasoning and find error or fault that dismisses my assertion. Ratch
 

thingmaker3

Joined May 16, 2005
5,083
At the risk of committing ad nauseum, I'm still waiting for your own evidence:

1) You've claimed the All About Circuits text is wrong, but have given no specific example, nor cited authoritative counterexample. Your silly Beaty link is no where near authoritative. Alwyrd's notions of "waste current" are leaky at best (pun intended).

2) You've echoed Beaty's extraordinary claim but shown no extraordinary evidence - you've only begged us to accept "explanation" as "evidence." No matter how far you stick your head into the sand, the burden of proof rests exclusively and entirely with YOU. We are required to prove nothing, as we are not trying to discredit accepted model. It is YOU who are claiming counter to accepted model, and therefore YOU who have to do the work. Get yourself a breadboard and some test equipment and stop making silly excuses! Your "reasoning" and "explanation" are hollow and useless without hard fact.

3) I apologize for missing the formula you presented in your morass of shreddings, dodges, and hyperbole. It is hard to find my own feet in this mess you've created. (See item #4.) Other members have already addressed your misunderstanding of this formula, and I need add nothing more.

4) Your cut-and-paste diversions have become tiresome, and serve only to obfuscate your lack of evidence. I call upon you to address these issues directly. If you are unable to state your case in a logical manner, please at least refrain from the arrogant dismissal & dissection of the thoughts of other members of this forum. Such behavior damages credibility.
 

Dave

Joined Nov 17, 2003
6,969
Intention is not the same as an explanation of associative relation.



I have no problem with the quoted paragraph from the e-book. But how does the e-book and your comment above relate to whether transistors are voltage or current controlled?
Pay attention; this part of the e-book is setting the authors intention with respect to underlying semiconductor physics of BJTs, or specifically as you mentioned in your first exchange on this with me (ref. here) the issue of depletion regions. Whether the BJT is voltage or current controlled is an irrelevance at this stage in the discussion.

Yes, I am familiar with Is and what it can do.

Yes, Is and all the things that influence it affect the collector current. So does Vt. But no one tries to send a signal into a transistor thermally, or by changing the size of the silicon slivers, or changing the doping. They do it by changing the BIG variable that really can be changed dramatically, Vbe. Whether they do it by setting the base current, or any other means, the Vbe will determine what the collector current will be.
In fact that is exactly what the large semiconductors manufacturers do in their design processes. The up shot of this is that they aim to set B such that they can set the Ib-Ic characteristic. They could design it such that these very variables are used to control Is; however Is from a practitioner's perspective, is difficult to qualify as a design parameter. It doesn't matter either way, B and Is both account for the same extenuating variables.

Coexistence does not mean dual control. If you can increase the collector current by changing the base current without changing the Vbe, then you have dual control. Otherwise the base current in a BJT is just a nuisance waste current proportional to the collector current.
If you have a current source to the base, for a constant Vbe, Ic will vary accordingly with Ib. Can I ask, does that mean that the BJT is not a voltage-controlled device? On a simple practical level, stick a rheostat on the base and vary the current into the base for a constant externally applied voltage (where the externally applied voltage here is the variable over which you have control) over the range to keep the b-e junction forward biased - Ib varies and accordingly so does Ic. In fact it is accurate to say that the rheostat modifies the actual voltage across the b-e junction, and this once again illustrates the inextricable link between Vbe and Ib.

The fundamental fact about current control is that the base current is a regulator (a regulator being by definition a mechanism of automated control) for the collector current; that is the function of Ib is to maintain the designated characteristic of Ic. Without Ib, there is no majority carrier replenishment in the base, and the minority injection into the emitter is altered; by virtue of the Kirchhoff's Current Law this will have a direct influence on the current across the transistor including Ic. You can argue about how Ib arises by virtue of, amongst several parameters, Vbe; however on a fundamental level it is the current that does the regulation. Don't believe me, hypothetically imagine we have a transistor where you can vary the width of the base - for a constant Vbe forward biasing the b-e junction, as the base varies, it is Ib that acts as the regulator for Ic (i.e. it is the control mechanism).

Yes, that is true. Design is simplified when advantage is taken of the proportionality of the collector current to the base current. I have no problem with that. I have a problem with the explanation of how a transistor works. What I have not seen proven is that a transistor is a current controlled device. So far, all I have seen are current manipulation methods which ensure a correct Vbe is applied.

Accurate for designing circuits, but not accurate to say that a transistor is a current controlled device. Ratch
For a transistor to work, it requires both Vbe and Ib. Depending on how you represent the model of the transistor you can create a device that is current-controlled via the parameter B, or a device that is voltage-controlled via the parameter Is (and T). The models are one and the same.

You obviously cannot accept the inseparability of Vbe and Ib, and the fact that you can convert the models and underlying mathematics for both voltage-controlled and current-controlled methods. Practitioners prefer the current-controlled model; physicists probably prefer the voltage-controlled model. The fact remains, when you get down to the basics, they fundamentally represent the same thing. If you think that is wrong, then I suggest you publish it.

Dave
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
thingmaker3,

At the risk of committing ad nauseum, I'm still waiting for your own evidence:

1) You've claimed the All About Circuits text is wrong, but have given no specific example, nor cited authoritative counterexample. Your silly Beaty link is no where near authoritative. Alwyrd's notions of "waste current" are leaky at best (pun intended).
And I am still waiting for you to describe how a transistor is a current controlled device when ultimately it is the Vbe that controls the collector current.

I have and still do claim that All About Circuits (ABC) is wrong about transistors being current controlled (CC) devices. I do acknowledge that ABC is correct in stating that design can be accomplished by using CC methods due to the porportionality of the base current with the collector current. However, that in itself does not PROVE that a transistor is a CC device.

As for Beaty and Aylward, you cite no credible evidence to discredit their claim and engage in ad hominem attacts on them. You appear more interested in the "authority" and accreditation of the messenger than the message itself. That is not good because it dismisses some new fact or insight that might be present.

2) You've echoed Beaty's extraordinary claim but shown no extraordinary evidence - you've only begged us to accept "explanation" as "evidence." No matter how far you stick your head into the sand, the burden of proof rests exclusively and entirely with YOU. We are required to prove nothing, as we are not trying to discredit accepted model. It is YOU who are claiming counter to accepted model, and therefore YOU who have to do the work. Get yourself a breadboard and some test equipment and stop making silly excuses! Your "reasoning" and "explanation" are hollow and useless without hard fact.
I asked you to evaluate their claim by what they present, not by how many degrees they have. So far you have not done so. No matter how many times you decry them, the message is still there, and that does not go away. You say that you are required to prove nothing. That is false. You state that a transistor is a CC device, so it is YOU who should prove it. So far all you have shown is that the base current is proportional to collector current. It is YOU who is making the original claim, so it is YOU who should be breaking out the breadboard and show it to be true. Don't excuse yourself with stock phrases like "everyone knows that", because it rings hollow when confronted with established hard fact knowledge.

3) I apologize for missing the formula you presented in your morass of shreddings, dodges, and hyperbole. It is hard to find my own feet in this mess you've created. (See item #4.) Other members have already addressed your misunderstanding of this formula, and I need add nothing more.
I shredded nothing, I dodged nothing, and I exaggerated nothing. I challenge you to prove I did any of those things. I also addressed all the comments of other members and am unsure which formula you are talking about (Sedra?). You still need to show where I, Beaty, and Aylward are wrong.

4) Your cut-and-paste diversions have become tiresome, and serve only to obfuscate your lack of evidence. I call upon you to address these issues directly. If you are unable to state your case in a logical manner, please at least refrain from the arrogant dismissal & dissection of the thoughts of other members of this forum. Such behavior damages credibility.
I don't understand what you mean. I have to cut and paste because I cannot copy a whole book or reference into a post. The snippet I submit IS my evidence. I have addressed the issue directly. Where is the missing logic? I only dismiss the thoughts of others when I think they are not correct in their facts or reasoning. You don't believe everything you read in this forum, do you? Credibility of the individual is damage by the individual by what s/he posts, not by me. Ratch
 

thingmaker3

Joined May 16, 2005
5,083
I don't understand what you mean. I have to cut and paste because I cannot copy a whole book or reference into a post.
This is an example of your misdirection and obfuscation. It is not your references you slash and shred, it is the commentary of the members here. [/quote]
Credibility of the individual is damage by the individual by what s/he posts, not by me. Ratch
It is your own credibility you are destroying by your poor debate tactics. Address the issues directly, and folk might begin to take you seriously.
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
beenthere,

Any experiments at all? Can't be all that hard to demonstrate some universal characteristic of all BJT's.
I don't have a lab, but a college professor once told me that at very, very, very low Vbe voltages, the BJT acts like a FET, because due to the virtual nonexistent base current at that low, low, low voltage, nearly all the injected carriers from the emitter get passed on to the collector. So the voltage at that low, low, low level is controlling the charges from the emitter with no base current present. Of course as Vbe becomes larger some of the injected charge carriers finally get diverted to become base current in proportion to the collector current. But it is still Vbe controlling the collector current. Ratch
 

beenthere

Joined Apr 20, 2004
15,819
Got a cite on published data? Could be interesting.

Even better - does this observation have any practical application? What would change the consideration in setting a bias network for the output A-B stage in a big audio amp, just as a for instance?

What I'm getting at is: Does any of this really matter? Has it any potential to remake electronics? Can this "waste current" you refer to be eliminated, leading to improved efficiency?

Making claims that your understanding is better and deeper than the majority of EE's is one thing. Doing something with it - besides talking - is something else. Can you walk the walk?
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
Dave,

Pay attention; this part of the e-book is setting the authors intention with respect to underlying semiconductor physics of BJTs, or specifically as you mentioned in your first exchange on this with me (ref. here) the issue of depletion regions. Whether the BJT is voltage or current controlled is an irrelevance at this stage in the discussion.
I hear you, it is irrelevant. However CC is still wrong even if it is of no consequence.

In fact that is exactly what the large semiconductors manufacturers do in their design processes. The up shot of this is that they aim to set B such that they can set the Ib-Ic characteristic. They could design it such that these very variables are used to control Is; however Is from a practitioner's perspective, is difficult to qualify as a design parameter. It doesn't matter either way, B and Is both account for the same extenuating variables.
You can talk all you want about how a BJT is designed and manufactured, but after it is made, Vbe controls its collector current.

If you have a current source to the base, for a constant Vbe, Ic will vary accordingly with Ib. Can I ask, does that mean that the BJT is not a voltage-controlled device? On a simple practical level, stick a rheostat on the base and vary the current into the base for a constant externally applied voltage (where the externally applied voltage here is the variable over which you have control) over the range to keep the b-e junction forward biased - Ib varies and accordingly so does Ic. In fact it is accurate to say that the rheostat modifies the actual voltage across the b-e junction, and this once again illustrates the inextricable link between Vbe and Ib.
No, I don't believe that Vbe will stay constant when Ib is varied with a constant current supply. It will change slightly to accomodate the increase in collector current. Whichever way you use to modify the base current to change the collector current, Vbe will follow and be the mechanism that controls the collector current.

The fundamental fact about current control is that the base current is a regulator (a regulator being by definition a mechanism of automated control) for the collector current; that is the function of Ib is to maintain the designated characteristic of Ic. Without Ib, there is no majority carrier replenishment in the base, and the minority injection into the emitter is altered; by virtue of the Kirchhoff's Current Law this will have a direct influence on the current across the transistor including Ic. You can argue about how Ib arises by virtue of, amongst several parameters, Vbe; however on a fundamental level it is the current that does the regulation. Don't believe me, hypothetically imagine we have a transistor where you can vary the width of the base - for a constant Vbe forward biasing the b-e junction, as the base varies, it is Ib that acts as the regulator for Ic (i.e. it is the control mechanism).
And I and the others are saying that Ib is not essential to control of the collector current. It is a unavoidable waste current that just happens to be proportional to the collector. If somehow the base current did not exist, as it does not in low, low, low Vbe values, then the emitter still provides current to the collector. I keep trying to say that the base current is a side effect and not necessary to the control of the collector current. If the width of the base could be modulated physically, there would still be a waste base current because of the Vbe present. The presence of base current does not prove or indicate base current control.

For a transistor to work, it requires both Vbe and Ib. Depending on how you represent the model of the transistor you can create a device that is current-controlled via the parameter B, or a device that is voltage-controlled via the parameter Is (and T). The models are one and the same.
Ib is always present in a BJT working in the active region. Its presence is inevitable but not necessary. Models have to account for it because it affects the rest of the circuit or they rely on proportional current representation. In a practical application no one controls a transistor by varying beta or saturation current unless they are making a thermometer. Ratch
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
thinkmaker3,

This is an example of your misdirection and obfuscation. It is not your references you slash and shred, it is the commentary of the members here.
As I said before, I separated the commentary, not slashed and shredded as you have claimed. However, because of your objections, I am now keeping the quoted commentaries together as paragraphs. I hope you find that satisfactory.

It is your own credibility you are destroying by your poor debate tactics. Address the issues directly, and folk might begin to take you seriously.
I take responsibility for my credibility. The quality of my debate tactics is for each to judge. As I intimated in my previous posts to you, your debate style appears to be more ad hominum than a cogent refutation of my arguments. Everyone is free to take me seriously or not. Ratch
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
beenthere,

Got a cite on published data? Could be interesting.
You mean about a BJT being a VC animal? Almost all the material does not emphasize that fact. But I am keeping my eyes open and doing some searching.

What I'm getting at is: Does any of this really matter? Has it any potential to remake electronics? Can this "waste current" you refer to be eliminated, leading to improved efficiency?
In most cases I would say it does not matter. The designs using BJTs are so facilitated by using the proportionality of Ib to Ic that no one gives it a thought. I would say that unless you are designing a logrithmetic amplifier or something exotic, you probably would not need to be aware of it. One can't eliminate the waste current in a BJT. The physics are against you. If you were to somehow do that, the beta of the transistor would be infinity.

Making claims that your understanding is better and deeper than the majority of EE's is one thing. Doing something with it - besides talking - is something else. Can you walk the walk?
Well, others have by going beyond BJTs with FETS, CMOS, and other alternative solid state devices. Those newer devices have removed a lot of applications from junction transistors. Ratch
 

studiot

Joined Nov 9, 2007
4,998
Haven't you folks been having fun while I've been having a glorious holiday out in the wilds, fencing with the Devil's Advocate?

1) Any physical quantity that can affect the operating conditions of a device can be used to 'control' it in some fashion, by varying that quantity.

2) As such you can control a transistor with a hairdryer or lightbulb. There are useful circuits based on either of these.

3) If you wish you can affect circuit values by forcibly altering (suitably) either voltage or current. If you wish to use current control you are not limited to the base. Many circuits, especially within integrated cicuits use emitter injection.

4) When you come to consider the frequency dependance it is aspects of curent flow within a transistor that control the behaviour, rather than inter-electrode voltages. This is also true of FETs. So from this point of view transistors are current controlled.

5) It is also true that historically transistors followed electronic valves, which they are quite different from. With valves the mechanism to use voltage electrodes to control the flow of current is quite obvious. With transistors, however, the melding of two current loops is more obscure. So there was a desire to promote a simplifying distinction.
 
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Thread Starter

Ratch

Joined Mar 20, 2007
1,070
studiot,

Haven't you folks been having fun while I've been having a glorious holiday out in the wilds, fencing with the Devil's Advocate?
Good to hear from someone else for a change.

2) As such you can control a transistor with a hairdryer or lightbulb. There are useful circuits based on either of these.
True, but thermal is slow. Photons are a substitute for Vbe.

3) If you wish you can affect circuit values by forcibly altering (suitably) either voltage or current. If you wish to use current control you are not limited to the base. Many circuits, especially within integrated cicuits use emitter injection.
This discussion is about BJTs.

4) When you come to consider the frequency dependance it is aspects of curent flow within a transistor that control the behaviour, rather than inter-electrode voltages. This is also true of FETs. So from this point of view transistors are current controlled.
To be precise, you should say charge flow, not current flow. What aspects, and what controls the charge flow? Interelectrode? We are not talking about tubes, CCDs or FETs. Transistors are voltage controlled because the Vbe is what changes the collector current regardless what the Ib is.

5) It is also true that historically transistors followed electronic valves, which they are quite different from. With valves the mechanism to use voltage electrodes to control the flow of current is quite obvious. With transistors, however, the melding of two current loops is more obscure. So there was a desire to promote a simplifying distinction.
What does the above paragraph mean with regard to what controls a BJT? Ratch
 

thingmaker3

Joined May 16, 2005
5,083
As I intimated in my previous posts to you, your debate style appears to be more ad hominum than a cogent refutation of my arguments. Everyone is free to take me seriously or not.
You see only what you wish to see. I will waste no more of my time with you. May your life be a good one.
 

Thread Starter

Ratch

Joined Mar 20, 2007
1,070
thingmaker3,

You see only what you wish to see. I will waste no more of my time with you. May your life be a good one.
I wish that were so.

Sorry you choose to drop out.

Thank you, it already is. Ratch
 

Dave

Joined Nov 17, 2003
6,969
You can talk all you want about how a BJT is designed and manufactured, but after it is made, Vbe controls its collector current.
Have you ever used a BJT in a real application? Suggesting such a proposition, I can only suggest that you have not.

Let me ask a simple question: voltage source connected to a light - is the light controlled (controlled being the act of being turned on) by the voltage of the source or current through the bulb?

No, I don't believe that Vbe will stay constant when Ib is varied with a constant current supply. It will change slightly to accomodate the increase in collector current. Whichever way you use to modify the base current to change the collector current, Vbe will follow and be the mechanism that controls the collector current.
So if the base current is modified by a current source (i.e. a current source to base), then a current will be controlling Vbe? That'll be current-control then won't it.

Consider a BJT with the base driven by a switch thrown resistor, R, tied to Vdd. Emitter to ground and collector driving a load tied to Vdd (which for arguments sake is greater than twice the forward voltage of the b-e junction). For a given value of R Ib will be determined by the resistor. Charge flow to the base (as you would prefer it be called) will then force Vbe to ~0.6V to forward bias the b-e junction (in fact the potential divider created by throwing the switch causes charge to flow into the base which in turn creates the potential divider across the b-e junction). Currents in the circuit, including Ic, will change accordingly. If R is changed to a different value, the charge flow to the base will increase/decrease accordingly and will force Vbe to ~0.6V - by virtue of the dependence of Ib on Vbe and vice versa it will force Vbe to a slightly different value as changes on Ib are reflected on Vbe. The fundamental point is that the control mechanism is provided by the current to the base which sets the circuits behaviour including, Vbe and Ic. No-one denies the fact that the BJT is voltage-controlled, implicated by the characteristic of Vbe, but it is equally current controlled. Mathematics and intuition support support this idea, as does the theoretical and practical analysis of many experts in this field.

And I and the others are saying that Ib is not essential to control of the collector current. It is a unavoidable waste current that just happens to be proportional to the collector.
I did you the honour of reading Beaty's article last night, and whilst I fully support his analysis on the voltage aspects of the BJT, he conveniently ignores the characteristic behaviour of the base-current, which allows him to come to the conclusion that you are stating here that Ib is a waste current. Of the two components that are important to the base-currents behaviour on the BJT, his ignorance of the requirement for Ib to be supplied to replace the base-majority-carrier due to recombination seems the most convenient - this parameter is paramount to the minority-carrier concentration gradient in the base. As the base dimensions are fixed at the time of manufacture, the only way to control and regulate this concentration gradient is through the component of Ib that replenishes the majority carrier - think about what would happen if you didn't replenish the majority carrier in the base, what becomes of the npn or pnp structure? Fundamentally do we have a transistor anymore? This is current control, and if I was being ignorant I could pretend that Vbe is a by product of Ib - it isn't, they are inextricably linked!

If somehow the base current did not exist, as it does not in low, low, low Vbe values, then the emitter still provides current to the collector. I keep trying to say that the base current is a side effect and not necessary to the control of the collector current. If the width of the base could be modulated physically, there would still be a waste base current because of the Vbe present. The presence of base current does not prove or indicate base current control.
I'm sorry but you are wrong. The base-current is a function of Vbe:

\(I_{b} = \frac{I_{s}}{\beta}e^{\frac{V_{be}}{V_{T}}}\)

Ib is a function of Vbe: no Vbe - no Ib, no Ib where there is no Vbe (looking at this from a purely control perspective, i.e. ignoring thermal effects and so forth).

If you ignore the need to replenish majority-carriers in the base, then you can deduce that the base-current is superfluous. However, you cannot ignore this function of the base-current.

Ib is always present in a BJT working in the active region. Its presence is inevitable but not necessary. Models have to account for it because it affects the rest of the circuit or they rely on proportional current representation. In a practical application no one controls a transistor by varying beta or saturation current unless they are making a thermometer. Ratch
You clearly don't want to accept the point that voltage-control through Vbe and current control through Ib are one and the same thing; how they differ is in their implementation. This is a notion supported by all the leading academics and practitioners on this subject. If you don't want to "believe" the BJT can be current-controlled (and I say "believe", because of in the face of overwhelming evidence, theory, and experimental citations to suggest to the contrary, and in the absence of any forthcoming experimental evidence on your part to disprove these, it necessitates a belief-system), then it is not my place to try and convince you differently.

At this point I feel that this discussion is neither interesting nor constructive. Given time, this is only going to march towards a debate on the sematics of what constitutes control and a protracted debate on cause and effect. I therefore have no personal interest in pursuing this topic further. My conclusion is that people should still refer to the BJT as a current-controlled (as well as a voltage-controlled) device, and that the information in the AAC e-book is both accurate and appropriate. If you believe the notion that the BJT is not current controlled under any circumstances and you have evidence to support your proposition, then I reiterate my advice to publish it.

Dave
 

bloguetronica

Joined Apr 27, 2007
1,541
thingmaker3,



I wish that were so.

Sorry you choose to drop out.

Thank you, it already is. Ratch
He probably has chosen to "drop out" because he realized that there was no point discussing with you (anyway, a very wise choice). Dave presented very strong points explaining why Beaty's theory about BJTs is not correct. What did you missed?

I guess it is a matter of personal taste then. You keep yours, I keep mine, and everyone is happy. If you like to see BJTs working that way, fine. It doesn't mean that they actually work like that, though.
 
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