"N channel" vs. "NPN" name confusion

[WarSim]

Well isn't it peachy that a first order convention has been over extended past its intended application.  With that information of course it is wrong where it is applied beyond first order.  Same goes for voltage control. 
Thanks for supporting my position with you repeating that you answered a first order question with a third order principal.  The "physical" model is introduced in second order and not significantly implemented until forth order. 
We have conventions for the same reason we have things like right hand rule, left hand rule , etc.  nobody needs to delve into the magnetic domain calculations and theories to make use of a motor and the like. 
There is a possibility that I assumed that you mentioned students being confused about BJTs as new students.  I assumed that by the time they are delving into the higher orders it should be clear why the convention is altered or how the non-convention has developed. 
You are pressing the physical model point and I am not going to discuss physics here.  If I want to make my point further than first or second order, I will write a paper on it.  I have said before I know allot of stuff but at this point in my life I want what I say to be just my opinion.  I stated my opinion, you disagree, I'm ok with that. 
In summary with your opinion that the current controlled device description of a BJT is more than a convention and the original question was something more than a first order question you are correct. 


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[langwadt]

Okay, so here's a basic question I can't find the answer to by googling... when they talk about N channel FET, what is the equivalent transistor of this in the other notation? Is it NPN or PNP? I.e. the "N" in "N" channel, what N is is this referring to in the other notation: NPN or PNP ?

NPN and PNP devices are bipolar junction transistors. N and P channel devices are field effect transistors.

Attempting to equate them will be as fruitful as trying to equate an egremont russett apple with a navel orange.

I don't see why, there are differences but also similarities 

It makes sense to know that the polarities of  NPN/NFET and PNP/PFET are the same
and the configurations that a common with bipolars are common with fets

[dannyf]

* Can you explain, for example, the function of the simple current mirror without using the voltage-control principle?

Why not? You can use bjt or fet to construct current mirrors so the answer is yes.

I don't know why it is so puzzling.

[macboy]

OMG!  Seriously!  I have never heard this voltage controlled BJT statement ever in 42 years.   
I haven't ever met a single designer of transistors nor thesis suggesting your statement. 
If you hadn't mentioned "students" I would not have replied.  But if there is a chance you are a teacher/instructor/prof summarizing a BJT is sometimes a voltage controlled device to explain a schematic.  I beg you to stop and research the physics more to come up with a better explanation. 


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I agree, it is a ridiculous statement, one from someone who doesn't understand the physics of how the devices work. Obviously, one can observe a varying base-emitter voltage with varying collector current. That does NOT imply that the collector current is controlled by base-emitter voltage. Correlation does not imply causation.

[WarSim]

OMG!  Seriously!  I have never heard this voltage controlled BJT statement ever in 42 years.   
I haven't ever met a single designer of transistors nor thesis suggesting your statement. 
If you hadn't mentioned "students" I would not have replied.  But if there is a chance you are a teacher/instructor/prof summarizing a BJT is sometimes a voltage controlled device to explain a schematic.  I beg you to stop and research the physics more to come up with a better explanation. 


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I agree, it is a ridiculous statement, one from someone who doesn't understand the physics of how the devices work. Obviously, one can observe a varying base-emitter voltage with varying collector current. That does NOT imply that the collector current is controlled by base-emitter voltage. Correlation does not imply causation.

Yes it is funny how a simplified statement created to remember the primary datasheet characteristic curve general shape has turned into a subject of such debate. 
Besides last time I checked there hasn't even been a consensus across the physics word on what the definition of current is.  .  Personally my definition is : it's the A in ohms law. 


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[lapm]

Yes it is funny how a simplified statement created to remember the primary datasheet characteristic curve general shape has turned into a subject of such debate. 
Besides last time I checked there hasn't even been a consensus across the physics word on what the definition of current is.  .  Personally my definition is : it's the A in ohms law. 


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Actually there is, what current is well defined.

http://www.si-units-explained.info/ElectricCurrent/

[WarSim]

Yes it is funny how a simplified statement created to remember the primary datasheet characteristic curve general shape has turned into a subject of such debate. 
Besides last time I checked there hasn't even been a consensus across the physics word on what the definition of current is.  .  Personally my definition is : it's the A in ohms law. 


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Actually there is, what current is well defined.

http://www.si-units-explained.info/ElectricCurrent/

I must be speaking an unknown language people are missing my points and jokes. 
Hint the smiley face means humor. 
There are perfectly good usable definitions for current.  The point is that the physics community can't agree on one. 
It seems if you can't say I disagree and propose a competing point of view within 5 seconds you booted out of the physicist club.  
Assuming we can agree on a frame of reference, how long a second is and what 5 is of course. 


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[LvW]

I agree, it is a ridiculous statement, one from someone who doesn't understand the physics of how the devices work.

Hi macboy - You must be very sure to give such a harsh answer.
Have you ever made up your mind to find out why RE increases the input resistances and/or how the tanh function for the diff. pair is derived?
Perhaps you have time to read some additional sources for completing your knowledge? Here are some of them - most probably more credible than me:

1.) Berkeley University (page 292, 8th line from the bottom and page 297, begin of chapt. 8.3)
www.eecs.berkeley.edu/~hu/Chenming-Hu_ch8.pdf
(„IB is an undesirable but inevitable side effect of producing IC
by forward biasing the BE junction“)

2.) Book Sedra-Smith, pages 8, 9, 11, 13, 15, 17, 30
http://www.csie.ntpu.edu.tw/~dalton/course/microelectronics/ch5.pdf

3.) Two answers from Winfield Hill (co-author "Art of Electronics")
http://cr4.globalspec.com/thread/68055/voltage-vs-current

4.) Stanford-University (see pdf attachement, top of second page)

Perhaps you are fair enough to revise your reply?
Regards
LvW

 

[LvW]

Lastly I believe the issue with explaining the offered ccts with the offered convention is you are mixing the different order conventions.  The convention of BJT are current controlled devices is a first order convention that happens to be useful in second order just like in first order a resistor is considered to be purely resistive and at higher orders their inductance and capacitance is taken into account. 

Hi warsim - I am afraid, it makes not too much sense to continue this discussion.
Perhaps we have a communication problem due to different languages.
(Quote: „I am not going to discuss physics here“). My question: Why not ? From the beginning, I spoke about physical effects - and you are stressing „conventions" of first and higher order only. I do not know any document, article or textbook which classifies the control mechanism of a BJT as a pure "convention" only.

I must admit that I am a bit disappointed not to see any answers to my pure technical and circuit-oriented questions in my posts#17 and #22. I think, we all are engineers and should be able and willing to answer technical questions?

OK - let`s stop the „discussion“ (unfortunately in most parts non-technical) and let me summarize:

1.) Up to now, I have seen not a single publication/textbook which contains some arguments against the voltage-control property of BJT`s  (simply stating it would be current-controlled is no counter argument).

2.) However, there are many circuit-based effects and examples (and I have listed some of them in post #17 and #22)  which can be explained using voltage-control only (and NOT on the basis of current-control). Unfortunately, no comments from your side.

3.) More than that, the technical fact of BJT`s voltage-control is emphasized by many serious and credible engineers/scientists (see some examples in my former post#33).

Now - every reader of this thread may create his own view.   

[dannyf]

I spoke about physical effects   

It is precisely the physical effects that dictate such devices to be current controlled rather than voltage controlled. a NPN works through electron combination at the b-c junction. So if you control the electrons flowing into the base, you have controlled the collector current. So this whole thing is current (=charge / time) driven or controlled.

the technical fact of BJT`s voltage-control is emphasized by many serious and credible engineers/scientists

Appeal to authority probably isn't the best argument in any discussion. There are just as many morons among "serious and credible" experts as they are among lay persons, regardless of how many books such experts may have published.

[LvW]

Appeal to authority probably isn't the best argument in any discussion. There are just as many morons among "serious and credible" experts as they are among lay persons, regardless of how many books such experts may have published.

Did you realize that this was only one of three arguments?
It would be interesting to learn how YOU would explain why a resistor RE increases the input resistance of a common emitter stage and/or how the tanh function of a diff. amplifier is derived?

[c4757p]

Oh, not this again.

It is precisely the physical effects that dictate such devices to be current controlled rather than voltage controlled. a NPN works through electron combination at the b-c junction. So if you control the electrons flowing into the base, you have controlled the collector current. So this whole thing is current (=charge / time) driven or controlled.

It's the carriers flowing across the BC junction which cause the transistor to conduct, but you don't get to push them across that junction yourself. I'd like to see how you plan to do that. (Possibly something involving voltage?) Applying a voltage between base and emitter draws carriers up from the emitter, and most pass to the collector because of device geometry. This is a result of the voltage across the BE junction. Applying current to the base does not force a proportional current to flow to the collector, it's the voltage that develops as a result of the current that pulls the carriers from the emitter.

Appeal to authority probably isn't the best argument in any discussion. There are just as many morons among "serious and credible" experts as they are among lay persons, regardless of how many books such experts may have published.

The EEVblog Fallacy: If an authority speaks, he must be wrong because something something appeal to authority.

[dannyf]

Did you realize that this was only one of three arguments?

It shouldn't be any part of a rigorous discussion. By itself, the fact that someone, however authoritative s/he is, approved of something doesn't make that something correct. It is correct only because it is correct, not because someone approved of it.

It would be interesting to learn how YOU would explain why a resistor RE increases the input resistance of a common emitter stage and/or how the tanh function of a diff. amplifier is derived?

I wouldn't mind giving it a shot, if you could tell me 1) how those questions and associated answers support your assertion or disproves the other side's arguments; and 2) what is "resistor RE" and "tanh function".

Explain it in as plain language as you can, or you don't understand it.

[LvW]

I wouldn't mind giving it a shot, if you could tell me 1) how those questions and associated answers support your assertion or disproves the other side's arguments; and 2) what is "resistor RE" and "tanh function".
Explain it in as plain language as you can, or you don't understand it.

(Nice wording).
I am very sorry for my assumption that you would know 1) the meaning of a resistor RE in a common emitter stage and 2) by what mathematical function the input-output characteristic of a BJT based diff. amplifier stage is described. My fault - sorry.   

[LvW]

It's the carriers flowing across the BC junction which cause the transistor to conduct, but you don't get to push them across that junction yourself. I'd like to see how you plan to do that. (Possibly something involving voltage?) Applying a voltage between base and emitter draws carriers up from the emitter, and most pass to the collector because of device geometry. This is a result of the voltage across the BE junction. Applying current to the base does not force a proportional current to flow to the collector, it's the voltage that develops as a result of the current that pulls the carriers from the emitter.

Yes - intentionally, I have tried to explain my view  not based on carrier physics (holes/electrons) but on application circuits and their behaviour. 

[WarSim]

Lastly I believe the issue with explaining the offered ccts with the offered convention is you are mixing the different order conventions.  The convention of BJT are current controlled devices is a first order convention that happens to be useful in second order just like in first order a resistor is considered to be purely resistive and at higher orders their inductance and capacitance is taken into account. 

Hi warsim - I am afraid, it makes not too much sense to continue this discussion.
Perhaps we have a communication problem due to different languages.
(Quote: „I am not going to discuss physics here“). My question: Why not ? From the beginning, I spoke about physical effects - and you are stressing „conventions" of first and higher order only. I do not know any document, article or textbook which classifies the control mechanism of a BJT as a pure "convention" only.

I must admit that I am a bit disappointed not to see any answers to my pure technical and circuit-oriented questions in my posts#17 and #22. I think, we all are engineers and should be able and willing to answer technical questions?

OK - let`s stop the „discussion“ (unfortunately in most parts non-technical) and let me summarize:

1.) Up to now, I have seen not a single publication/textbook which contains some arguments against the voltage-control property of BJT`s  (simply stating it would be current-controlled is no counter argument).

2.) However, there are many circuit-based effects and examples (and I have listed some of them in post #17 and #22)  which can be explained using voltage-control only (and NOT on the basis of current-control). Unfortunately, no comments from your side.

3.) More than that, the technical fact of BJT`s voltage-control is emphasized by many serious and credible engineers/scientists (see some examples in my former post#33).

Now - every reader of this thread may create his own view.

Here is my answer to all your questions to me.  You are an argumentative arse. 

You are creating a disagreement where there isn't one.  I have said ,in your context, following the papers you have given, you are correct.  You have repeatedly demanded that I play the papers war because the papers I subscribe to vary from the ones you cited.  I do not want to discuss why the differences between the various physicist or EE papers.  In my prior comment I mistakenly assumed you would want to investigate the opposing papers. Your next response proved it was a waisted response.  Lastly if the paper or research brief is more that 7 years old I read it.  If it is newer I haven't, I stopped caring. 

My one request was stop confusing people new to electronics with such papers.  Two statements where made to help remember the shape of their primary characteristic curve back when transistors where new.  They are BJTs are current control MOSFETs are voltage control.  Because the primary datasheet characteristic curves are Ibe/Ice and Vg/Ids.  It was/is a memory helper only, ergo a convention.  This is the basic answer for a basic question asked by the OP. 

I don't give a ---- if a learned Doctor hijacked the phrase.  Nor do I care if a few papers exist that makes it unsupportable in higher orders.  The fact is almost every beginner only needs the basics, and wholly relies on spice for anything more detailed.  For crying out loud I have seen EEs go down this route.  It doesn't flipping matter! 

I am convinced that you are not a doctor.  Therefore have no right to dictate how I express my understanding.  No, I am not a doctor but the people who have accepted me as a peer are.  Frankly any doctor would be an idiot not to at lease consider the thoughts of anyone in the top 2 percentile IQ.  Seven years ago I got tired of the constant debates and now I don't care if anyone disagrees with me.  If I personally encounter something I don't understand I will figure it out.  Until then I am out of the papers game.   

If such arguments are your hobby you will have one for life.  There are many more devices coming that will offer many more opportunities for you to debate/orate with/to the unwilling.  If you do have a high IQ I strongly urge you to find a group that loves to debate.  Ie genius join Mensa, gifted join councils, etc.  Just stop trying urge me into debating the merits of papers. 


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[LvW]

You are an argumentative arse. 
...............
You are creating a disagreement where there isn't one. 

Maybe it is good that English is not my native language- so I do not understand all the intricacies of your reply.
I am really surprised and disappointed about the style and the tone of this debate.
Are we really engineers/lecturers who - controversely - are discussing technical matters?   

As I have mentioned, I will not resume the discussion - however, for my opinion you have, indeed, expressed your severe disagreement:

Quote: "OMG! Seriously! I have never heard this voltage controlled BJT statement ever in 42 years. 
I haven't ever met a single designer of transistors nor thesis suggesting your statement.
.........................
I beg you to stop and research the physics more to come up with a better explanation.

Well - I did follow your recommendation and I have tried to explain/justify my position in the subsequent posts. 
If there was no disagreement between us - where did you express your agreement as far as the main question is concerned (voltage vs. current control)? 
Perhaps, I missed something, and - as I have indicated already - it is possible that "language problems" are responsible. If this should be the case - sorry, my fault.
On the other hand - a short comment from your side to some of my technical examples/questions could have perhaps made the the situation somewhat clearer.   
Regards
LvW

[WarSim]

One more time. 
When I assumed you where using the term current controlled device as intended when the phrase was initially coined as a primary characteristic curve descriptor as a learning/memory tool for first order questions your response was wrong. 
When I realized that your response was just inappropriate I said so.  I tried to explain that I did not like it when you answered a first order question with a statement referencing the physics of the physical model.  If you want to help answer the OPs question answer their question appropriately.  If you want to debate the physical model then start a thread for that purpose.  Hijacking this thread for this debate is considered rude by accepted forum behaviour.   
Because of the papers you have cited in support of your position it would require referencing other papers and detail why the answer of the others are also deemed valid.  This is where I refused, but you keep prodding.  This prodding is why I am annoyed.  This is why you are getting negative responses from me. 
 


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[Zero999]

There's always an argument when this crops up.

Anyway, here's how I prefer to explain why the input impedance of an emitter follower is high.

[dannyf]

why the input impedance of an emitter follower is high.

Because of the current feedback - in the sense that the collector current goes through the emitter resistor.

All you need is to take a look at the small signal model for a bjt: on the output side, it is a current sink, controlled by the base current (aka current-controlled current sink).

The typical small signal model describes the input as a (variable) resistor, and the output current varies with the input current (=base current).

The original question has zero bearing on if a device is current- or voltage-controlled and is totally irrelevant to this discussion.

[hamdi.tn]

is that some kind of obsession to make things way more complicated ... it's  simple Ic = beta Ib , a discussion longer than some ppl life story with an absolute confidence that current control is FALSE 
Innocent question cause i have to take the opportunity to ask irrelevant question in a totally irrelevant discussion to the OP question  is a diode or a LED a current control device or a voltage control device, where datasheet clearly show led as CC device, it will not pass current until the voltage rich certain level , so it must be voltage control too .. blow my mind   

[dannyf]

Ic = beta Ib

Not so simple. All that says is how beta is defined, not how Ic changes with Ib.

The same with Ohm's law - it is used to define resistance, not to define voltage / current from current / voltage across a resistor.

[LvW]

  If you want to help answer the OPs question answer their question appropriately. 

Perhaps you have overlooked that I have answered the OP`s question in my post#6.
But I agree with you - it would have been better to open a new thread for dicussing the BJT control mechanism.
Why didn`t you come up with this earlier?

[WarSim]

  If you want to help answer the OPs question answer their question appropriately. 

Perhaps you have overlooked that I have answered the OP`s question in my post#6.
But I agree with you - it would have been better to open a new thread for dicussing the BJT control mechanism.
Why didn`t you come up with this earlier?

Yes you did, reply 6 post 7 was a great answer.  And the OP thanked you for it. 

I did imply not here a little earlier, but I agree my position on this point was not stated clearly stated.  Communication is a tow way street so I will share blame in this. 


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[LvW]

If you want to debate the physical model then start a thread for that purpose.  Hijacking this thread for this debate is considered rude by accepted forum behaviour.   

Warsim - after having some time (over night) to think about your personal accusations I cannot resist to reply as follows:
The OP`s question was if there are some commonalities between BJT`s and FET`s. And, I think, in this context it is NOT a "rude hijack" to bring up the question:
"Is the BJT current-controlled or voltage-controlled (like the FET)?". Did I really violate forum rules in a rude manner? I don`t think so.     
(By the way: There was a discussion - post 30...32 - in which you took part about the definition of current; ...Hijack?).