thingmaker3,

"Current flow" is indeed a redundant term. I'm not fond of the phrase "ATM machine" as it is also redundant. But you don't see me insisting the banks all change their ways.

A truthful acknowledgment is all that is required.

None of the "meat" (what little of it there is) in Beaty's material on charge is anything new. He embellishes this with smoke and mirrors - simply holding up common semantic practice as a straw-man argument while launching ad-hominem attacks at an undefined "them" and "they."

He believes that there is confusion about what charge and current mean. Especially for beginners.

simply holding up common semantic practice as a straw-man argument while launching ad-hominem attacks at an undefined "them" and "they."

As long as he does not get personal.

Beaty is in love with the embellishment of the argument.

Perhaps, but it does not make what he is saying false.

The argument itself is contained in most textbooks.

Which argument are we talking about now?

I've no clue why Beaty (and others) are unable to go from "current is a flow of charge carriers" and "current density is proportional to conductivity and electric field" to

He and I have no problem with that.

"base current times Hfe equals collector current." Maybe they didn't read the text books as well as they thought they did."base current times Hfe equals collector current." Maybe they didn't read the text books as well as they thought they did.

Because the true mechanism for controlling the collector current is Vbe. As the equation in Sedra and Smith shows. The beta can vary all over the map, as it does at different frequencies and Q points, but as long as you keep Vbe steady, the emitter current will not change. That makes a BJT a voltage controlled device. Ratch

 

as long as you keep Vbe steady, the emitter current will not change. That makes a BJT a voltage controlled device. Ratch

Steady Vbe means steady base current. That makes the BJT a current controlled device.

 

All one really need do is look at some characteristic curves to see the BJT is current controlled.

 

Figure 16: http://web.mit.edu/6.301/www/2N3904o.pdf

Figure 14: http://www.onsemi.com/pub_link/Collateral/2N3906-D.PDF

Figure 9: http://www.onsemi.com/pub_link/Collateral/TIP120-D.PDF

I could do this all night, but dinner is ready and I have more entertaining plans for the evening.

 

thingmaker3,

Wrong. That is the common and accepted (by everyone except you and Beaty) model. It is the model used by Intel, Texas Instruments, and a host of other manufacturers who's products work exactly as the model predicts

The transistor works in spite of their model if they believe it is a current controlled device. It could just as well be said that their transistors work because of Beaty's model also.

That has to do with the relationship between EMF, resistance, and current

Which in turn has to do with the nonlinear physics of the junction diode.

but you don't believe in EMF either, do you? How convenient for you.

EMF being voltage. What an outrageous idea. Of course I believe in voltage. Ratch

 

beenthere,

Perhaps we could confine this to the current question. This is a very early assertion of Beaty's, and I think we can let the remainder stand or fall on just this point. Legalisticaly, that will be falsibus in uno, falsibus in omnes (unless I've misremembered another Latin tag). That might be rendered as: false in one thing, false in all things.

So - does Beaty disprove the notion of current?

Of course he recognizes current. But he does not approve of using "current traveling", "current flowing", or "current movement." One should use the term charge instead. That was explained before in this thread. You are looping if you are asking this question again. Also he is explaining current so he can more clearly put forth his arguments about the transistor being a voltage controlled device. His current (charge movement) definition explanation has nothing to do with whether he is right or what controls a transistor. Just on general principles, it is wrong to assert that because one is wrong about one thing, one is wrong about another--at least without showing the linkage. No amount of Latin pablum can change that. Ratch

 

thingmaker3,

But we must not decree "correct in one thing, correct in all things."

That is self-evident. Things should be proven.

Beaty then goes on with extensive "water analogy" use. Water analogy has been dismissed even by Ratch himself.

He is not using it to show transistors are voltage controlled. He is using it to illustrate a parallel bad semantic reference. That use of a water description is a good example which drives home his point about lexical usage.

Next comes some nonsense about "uncharged charges." Beaty shows again that his problem is limited solely and exclusively to semantics. He decires the (admittedly) poor semantics of others while himself spewing non-sequiturs and force entendres. Please not I am not making a tu quoqu claim - I am simply decrying Beaty's inability to divorce his argument from his passion.

He is talking about mobile charges (electrons) in metals which have a charge but are balanced by the metal ions for a net charge of zero. He does call them cancelled charges later. It has nothing to do with whether he is right about voltage control or whether he is passionate and whether passion makes any difference for his argument. Ratch

 

thingmaker3,

Steady Vbe means steady base current. That makes the BJT a current controlled device.

No, it does not. Base current is dependent on beta, which can be all over the place with respect to frequency and Q point. The equation for Ic with repect to Vbe does not include beta. The base current is an effect, not the cause of collector current for BJT operation in the active mode. The Vbe is really what controls the carrier injection into the base, and thereafter onwards to the collector current. Ratch

 

thingmaker3,

All one really need do is look at some characteristic curves to see the BJT is current controlled.

Which configuration? Which curve? Does it show that the collector current can change when Vbe stays the same? Ratch

 

thingmaker3,

Figure 16: http://web.mit.edu/6.301/www/2N3904o.pdf

Figure 14: http://www.onsemi.com/pub_link/Collateral/2N3906-D.PDF

Figure 9: http://www.onsemi.com/pub_link/Collateral/TIP120-D.PDF

I also have tons of transistor specs. What does it prove? The beta parameter is all over the map, varying as much as 300%. But if the Vbe is held constant, then the collector current will not change no matter what the beta happens to be.

I could do this all night, but dinner is ready and I have more entertaining plans for the evening.

C'mon back when you are finished. Ratch

 

cumesoftware,
Why is that? How do you explain the dependence of Ic on Vbe in the equation I posted from Sedra & Smith in my reply to Dave 3 or 4 messages ago?

Have you noticed that a BJT is like two diodes in series. And have you notice that the collector current/base current resembles the I/V curve of a diode? The I/V curve is natural because the depletion layer doesn't disappear in a uniform way. At 0.6V some holes on the depletion layer start appearing. If you increase the voltage a bit the depletion layer holes are more frequent, thus allowing more current to pass. If the depletion layer disappeared evenly, the I/V curve would be two straight lines.

You are mistaken. The only way to pass no current through a diode is to bias it to zero. Below the 0.6-0.7 volts for a silicon diode, the current drops precipitously, but it does not go to zero until Vbe becomes zero. Above 0.6-0.7 volts it increases very fast. This is because the V-I curve of a forward diode is exponential, as illustrated in equation from Sedra & Smith shown earlier. That shows that a transistor is a voltage controlled device even when current is present and proportional in the base circuit.

What! And what about the potential barrier effect? Don't forget that on a diode, some energy is spent don taking out the electrons from the barrier that naturally forms between N and P silicon. A depletion layer is naturally formed when those materials are in contact and it behaves like pure silicon, because there are no holes and no excess electrons in that area. The potential barrier is like a 0.7V battery in reverse and in series with some load. The depletion layer must disappear before electrons start to flow.

What parts of Mr. Beaty's explanation (not theory) don't you understand?

I do understand them. It doesn't requires a genius to understand that. First, charge doesn't move along a wire. There are no flows of charge. Electrons ere the one doing that. If charge moved along a wire, one end of the wire would be positively charged while another end of the wire would be negatively charged. That happens in capacitors. Due to the submission of an isolator to a voltage, positive charge moves to one side and negative charge moves to another. However, electrons don't flow through capacitors, unless the capacitor disrupts, that is, it is destroyed by excess of voltage. That is a flaw. Anyone who took an electrical engineering or a physics degree should know that. However I didn't took none and I know.
Plus, as I tried to explain you before, BJTs are not voltage controlled devices. The illusion that they are is created by the fact that at 0.6V there is no current, while at 0.7V there is a lot of current, and at 0.9V you saturate the transistor. That is an illusion created by the emitter diode that has a I/V curve like any other diode.

Let's stay on topic. Creationism has no relevance to theory of operation of BJTs.

Hovind calls himself a doctor too and his theory has many holes as well. See the resemblance?

Would you explain that more clearly? As long as you keep the diode current below the max level, you are OK. The way to do that is to insert resistance in series with the diode.

Exactly my point. You agree that you are controlling te current and not the voltage of a LED. But since, for example a typical red LED drops 1.95V at 10mA and 1.98V at 15mA, one can argue that the brightness on the LED is controlled by voltage, where actually is controlled by current, since more current = more holes and electrons recombinating per second = more photons emitted per second = more intense light. Plus, all LEDs have different curves. That is the kind of flaw that Beaty is committing right now.

Very little due to the exponential I-V curve.

Very little, yes. But the curve is not exponential. The current is zero for a whole range of voltages due to the barrier potential. Plus the depletion layer doesn't allow any flow of electrons while is there. It must have a hole to allow current to pass. A thin depletion layer allows as much current as a thick one: zero current. Beaty says otherwise.

Feedback can be used to make Q point stable despite variations of parameters.

These characteristics are not inherent to BJTs themselves, but caused by the external resistor network. You should know that and we are not discussing Q points anyway.

As are BJTs. Ratch

Noooooooo! Wrong! Try again. You can't feed the base of A BJT without a resistor. PLUS, BJTs have a significant draw of current though the base that depends on the emitter-collector current as well, which means that they are current controlled devices more that they are voltage controlled devices. Plus, they need a resistor in order to prevent them for oversaturating, or else current will only get the emitter diode, thus causing the transistor to act as a rectifier. FETs, unlike BJTs, are true voltage controlled devices. The current biasing a FET is proportional to the voltage at the gate, that can vary from GND to Vcc. The fact is that it is impossible to oversaturate a FET by connecting its gate to the rails. Of course that might be some current through the gate, but by definition, it needs none, since the gate is isolated from the rest of the FET.

 

thingmaker3,



Which configuration? Which curve? Does it show that the collector current can change when Vbe stays the same? Ratch

Let's turn that around - can you or Beaty demonstrate that bipolar junction transistors are purely controlled by voltage? You do realize that it implies current plays no part when you assert control by voltage.

Can you take, say, a 2N2222A and make a test setup that shows that it is solely the voltage difference between the base and the emitter that controls collector current? Can you do it with the emitter led straight to ground? Can you show no current in the BE junction (remember that any current change there means that voltage is not the control mechanism)?

Having done that, can you do the same with every other BJT? PNP, NPN, epitaxial, mesa, planar, silicon, germanium, etc? A blanket assertion requires extraordinary effort to justify.

By the way - that also requires single PN junctions to be voltage controlled. Think anybody can demo that on a 1N34? Might have to work in the dark to keep those stray photons from causing current. For that matter, what is the mechanism that lets me grind the top off a TO-5 can and use a 2N404 as a phototransistor? Photons surely don't carry charge?

 

I also have tons of transistor specs. What does it prove?

It proves the transistor is a current controlled device, no matter how blithely you try to dismiss it.

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.

2) You've echoed Beaty's extraordinary claim but shown no extraordinary evidence - you've only begged us to accept "explanation" as "evidence."

3) You've spouted the names "Sedra and Smith" implying one of their formulas support your extraordinary claim, but have not shed light on which formula you hint at.

 

To Ratch:
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.

 

OK, I will acknowledge that correction. What is not always stated when Bell Labs is credited with the invention of the transistor was that it was a point contact junction transistor.

The creditation given in the e-book is accurate.

Yes, but it is not tied into the introduction of the BJTs and its importance is not mentioned therein.

The e-book introduction states the authors intention very clearly:

My intent here is to focus as exclusively as possible on the practical function and application of bipolar transistors, rather than to explore the quantum world of semiconductor theory. Discussions of holes and electrons are better left to another chapter in my opinion. Here I want to explore how to use these components, not analyze their intimate internal details. I don't mean to downplay the importance of understanding semiconductor physics, but sometimes an intense focus on solid-state physics detracts from understanding these devices' functions on a component level. In taking this approach, however, I assume that the reader possesses a certain minimum knowledge of semiconductors: the difference between "P" and "N" doped semiconductors, the functional characteristics of a PN (diode) junction, and the meanings of the terms "reverse biased" and "forward biased." If these concepts are unclear to you, it is best to refer to earlier chapters in this book before proceeding with this one.

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.

A concensus of agreement does not always lead to correct knowledge. I submit that in this case it does not. I own a copy of Microelectronic Circuits by Adel Sedra and Kenneth Smith, both of the University of Toronto, third edition. On page 196, the equation for the collector current is Ic=Is*exp(Vbe/Vt) where Is is the saturation currect and Vt is the thermal voltage. A similar equation exists for the emitter current which is usually close to the same value. On page 197 under Recapitulation they say, "We have presented a first-order model for the operation of the npn transistor in the active mode. Basically, the forward-bias voltage Vbe causes an exponentially related current Ic to flow in the collector terminal." That is what Beaty and myself agree upon.

The review panel is, but not Sedra and Smith. I don't know about the other two references you gave, because I don't have them handy.

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).

Now lets look at the notion of current-controlled current embodied in the following:

Ic = BIb.

Where the collector-current, Ic, is the controlled current, and the base-current, Ib, is the controlling current. Forget that you disagree with this conclusion at the moment.

You will note from the work of Sedra and Smith in their treatise of the base current that the common-emitter current gain parameter, B, is a parameter of a function of the transistor physicality's (namely the width, length, and areas of the transistor geometry), doping concentrations, carrier diffusivity, and operational conditions (namely the minority-carrier lifetime, which in turn is a function of the temperature).

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.

Whilst we are dealing with the Sedra and Smith treatise on the BJT (incidentally I have the 5th edition) perhaps we could take a look at the rest of their recapitulation on the BJT:

The current of the controlled source, which is equal to the collector current, is controlled by Vbe according to the exponential relationship indicated, This model is in essence a non-linear voltage-controlled current source. It can be converted to the current controlled current source shown in Fig 5.5(b) by expressing the current of the controlled source as alpha*Ie (where alpha is the common-base current gain).

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.

In your words, "Sedra and Smith are right".

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. There massively acclaimed text Art of Electronics describes traditional methods as, and I quote, "...unnecessarily complicated and unintuitive", citing the "elaborate equations" used as a barrier. There 4-step model of the current amplifier came to the conclusion: "A small current flowing into the base controls a much larger current flowing into the collector". The design models that are proposed in Art of Electronics are the very models that are used by the large semiconductor manufacturers in designing circuits, and by EEs developing BJT circuits application (not some of the examples given here in this thread).

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:

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.

Dave

 

comesoftware,

Sorry I am so late in answering this, but I had some less enjoyable but more essential tasks to perform.

Have you noticed that a BJT is like two diodes in series.

They are often shown that way, but you won't get a transistor doing that. The dopings would be wrong and the physical contact and correct size dimensions are missing. Why is this relevant?

And have you notice that the collector current/base current resembles the I/V curve of a diode?

No, I have not noticed that at all. See the link below which shows the I/V curve of a diode, and tell me that when you plot Ic/Ib, the curve looks similar.

The I/V curve is natural because the depletion layer doesn't disappear in a uniform way.

The depletion layer becomes thinner and thicker, but it never disappears.

At 0.6V some holes on the depletion layer start appearing.At 0.6V some holes on the depletion layer start appearing.

Holes from where? If charges start appearing in the depletion layer, it would not be a depletion layer, would it?

If you increase the voltage a bit the depletion layer holes are more frequent, thus allowing more current to pass.

The emitter-base voltage thins the depletion layer so that charges can can move from the emitter to the collector more readily. That is why the real mechanism of collector current control in a transistor is Vbe.

Originally Posted by Ratch
You are mistaken. The only way to pass no current through a diode is to bias it to zero. Below the 0.6-0.7 volts for a silicon diode, the current drops precipitously, but it does not go to zero until Vbe becomes zero. Above 0.6-0.7 volts it increases very fast. This is because the V-I curve of a forward diode is exponential, as illustrated in equation from Sedra & Smith shown earlier. That shows that a transistor is a voltage controlled device even when current is present and proportional in the base circuit.


Answered by comesoftware
What! And what about the potential barrier effect? Don't forget that on a diode, some energy is spent don taking out the electrons from the barrier that naturally forms between N and P silicon. A depletion layer is naturally formed when those materials are in contact and it behaves like pure silicon, because there are no holes and no excess electrons in that area. The potential barrier is like a 0.7V battery in reverse and in series with some load. The depletion layer must disappear before electrons start to flow.

The depletion becomes thinner and never completely disappears. Also charges flow even when the voltage is below 0.7 volts for silicon. Here is a link for the I/V curve of a diode. http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/passive/diode/chars/chars.htm Notice current is present anytime forward voltage is > 0. It also gives the diode equation, which shows the exponential relationship of diode I/V.

First, charge doesn't move along a wire. There are no flows of charge.

Huh? How can you have current without charge movement?

Electrons ere the one doing that.

But electrons are charge carriers. You just said that charge does not move along a wire.

If charge moved along a wire, one end of the wire would be positively charged while another end of the wire would be negatively charged.

Of course not. When one charge leaves one end of the wire, another enters from the other end, thereby equalizing the net charge.

That happens in capacitors. Due to the submission of an isolator to a voltage, positive charge moves to one side and negative charge moves to another. However, electrons don't flow through capacitors, unless the capacitor disrupts, that is, it is destroyed by excess of voltage. That is a flaw. Anyone who took an electrical engineering or a physics degree should know that. However I didn't took none and I know.

Who is talking about capacitors?

Plus, as I tried to explain you before, BJTs are not voltage controlled devices.

Your explanations fall flat.

The illusion that they are is created by the fact that at 0.6V there is no current, while at 0.7V there is a lot of current, and at 0.9V you saturate the transistor. That is an illusion created by the emitter diode that has a I/V curve like any other diode.

As the link shows, current is present anytime the forward diode voltage is > 0. Current starts to become significant at 0.7 volts according to the diode equation. You are wrong to keep saying that no current is present below 0.7 volts.

Hovind calls himself a doctor too and his theory has many holes as well. See the resemblance?

No.

Originally Posted by Ratch
Would you explain that more clearly? As long as you keep the diode current below the max level, you are OK. The way to do that is to insert resistance in series with the diode.

Answered by comesoftware
Exactly my point. You agree that you are controlling te current and not the voltage of a LED. But since, for example a typical red LED drops 1.95V at 10mA and 1.98V at 15mA, one can argue that the brightness on the LED is controlled by voltage, where actually is controlled by current, since more current = more holes and electrons recombinating per second = more photons emitted per second = more intense light. Plus, all LEDs have different curves. That is the kind of flaw that Beaty is committing right now.

Limiting the current is not the same as saying that Vbe does not control the collector current. You are confusing the method of how Vbe is controlled with whether it is the real mechanism for controlling Ic. There is no flaw in Beaty's reasoning.

Originally Posted by Ratch
Very little due to the exponential I-V curve.Originally Posted by Ratch
Very little due to the exponential I-V curve.

Answered by comesoftware
Very little, yes. But the curve is not exponential. The current is zero for a whole range of voltages due to the barrier potential. Plus the depletion layer doesn't allow any flow of electrons while is there. It must have a hole to allow current to pass. A thin depletion layer allows as much current as a thick one: zero current. Beaty says otherwise.

Wrong, wrong, wrong. The curve is exponential, the link above with the diode equation proves it. The depletion region reduces the current when the Vbe forward voltage is above zero, but it does not stop it. The thickness of the depletion region varies the collector current. And the thickness of the depletion varies with the Vbe. Beaty is right about this. Everyone knowledgeable about transistor operation knows this. Vbe controls the collector current. I already flashed an equation from Sedra and Smith showing that fact in a previous post.

These characteristics are not inherent to BJTs themselves, but caused by the external resistor network. You should know that and we are not discussing Q points anyway.

The variation of beta and other transistors are inherent to the transistor, but the feedback to reduce these variation come from the external circuitry. Nothing I said contradicts this.

Noooooooo! Wrong! Try again. You can't feed the base of A BJT without a resistor. PLUS, BJTs have a significant draw of current though the base that depends on the emitter-collector current as well, which means that they are current controlled devices more that they are voltage controlled devices. Plus, they need a resistor in order to prevent them for oversaturating, or else current will only get the emitter diode, thus causing the transistor to act as a rectifier. FETs, unlike BJTs, are true voltage controlled devices. The current biasing a FET is proportional to the voltage at the gate, that can vary from GND to Vcc. The fact is that it is impossible to oversaturate a FET by connecting its gate to the rails. Of course that might be some current through the gate, but by definition, it needs none, since the gate is isolated from the rest of the FET.

None of the above proves the transistor is a current controlled device. It only shows that the collector current is proportional to the base current, not that the base current controls the collector current.

Perhaps a story will illustrate what I am talking about. A town starts small and grows larger. A running census is made, but it starts to become expensive. So the city engineer says to the mayor, "look at these figures. When the town's population doubled, so did the waste treatment we had to process. Why search out and count everyone, when all we have to do is monitor the throughput of the waste treatment plant." However no one ever said that by not treating the waste water could they control the population. What I am trying to say is that the cause is the Vbe and the effect is the Ib, because that is the waste current of the transistor. Folks design transistor according to the waste current it will produce because they know that the waste base current is proportional to the collector current. The more insightful folks know that the real control mechanism is the Vbe voltage. Ratch

 

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.....

 

beenthere,

Let's turn that around - can you or Beaty demonstrate that bipolar junction transistors are purely controlled by voltage?

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

You do realize that it implies current plays no part when you assert control by voltage.

Not quite true. The collector current is proportional to the wastage of the base current. That is useful.

Can you take, say, a 2N2222A and make a test setup that shows that it is solely the voltage difference between the base and the emitter that controls collector current?

Yes, after factoring out the thermally Icbo current that will pass through the CB junction.

Can you do it with the emitter led straight to ground?

Yes, but I would have to be careful not to burn out the EB junction.

Can you show no current in the BE junction (remember that any current change there means that voltage is not the control mechanism)?

There will be current in the base circuit if I apply voltage to the BE junction. It is waste current that does not control the collector current, but is proportional to collector current. Your statement above is wrong. The control comes from Vbe.

Having done that, can you do the same with every other BJT? PNP, NPN, epitaxial, mesa, planar, silicon, germanium, etc? A blanket assertion requires extraordinary effort to justify.

Yes, every BJT will be controlled by the Vbe. All those other names you rattled off are simply different manufacturing methods and materials that enhance certain BJT parameters. Their basic behavior will be the same.

By the way - that also requires single PN junctions to be voltage controlled. Think anybody can demo that on a 1N34?

The current of a diode is expressed by the diode equation which I flashed to comesoftware in a previous post. That relates current to the voltage across the diode. The diode equation applies to all junction diodes including 1N34's. Is that what you mean by control?

Might have to work in the dark to keep those stray photons from causing current. For that matter, what is the mechanism that lets me grind the top off a TO-5 can and use a 2N404 as a phototransistor? Photons surely don't carry charge?

The photons supply energy, not charge to the junction, thereby changing the energy level of the conduction band. It is similar to applying a voltage or heat to a junction. Ratch

 

beenthere,



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



How conveniently inconvenient. So no method can be described? We just take your word for it?

 

thingmaker3,

It proves the transistor is a current controlled device, no matter how blithely you try to dismiss it.

How? I see so proof in those graphs unless you point it out.

1) You've claimed the All About Circuits text is wrong, but have given no specific example, nor cited authoritative counterexample.

Wrong on three things. I linked to Beaty, who you have not proven wrong. I also linked to Kevin Alysworth, who has an expert knowledge on such matters. (see his biography). Furthermore, I linked to Sedra and Smith in a previous post which I guess you did not read or ignored. I will repeat Sedra's quote again.

"We have presented a first-order model for the operation of the NPN transistor in the active mode. Basically, the forward-bias voltage Vbe causes an exponentially related current Ic to flow in the collector terminal."

2) You've echoed Beaty's extraordinary claim but shown no extraordinary evidence - you've only begged us to accept "explanation" as "evidence."

I asked you all to show where he is wrong. It should not take a physics lab to do that, right. So far, I have not heard anything of consequence that disproves what he asserts.

3) You've spouted the names "Sedra and Smith" implying one of their formulas support your extraordinary claim, but have not shed light on which formula you hint at.

I did give the formula from his text. It can be found elsewhere too. Here it is again one more time.

Ic = Is*exp(Vbe/Vt) where Is is a constant called the saturation current and Vt is the thermal voltage.

Notice that Ic is dependent on Vbe, which is what Beaty, Alyward, and I aver. No one so far has explained this dichotomy between that formula and your current control claim. Ratch