The beta model isn't even suitable for under-tens to study. Sooner or later the OP will discover it falls apart in certain circumstances. Then some kind soul will introduce him to Ebers-Moll and the transconductance model and he will damn your hide for spinning him such snake-oil early in his studies.
-- LOL! So what's good for the goose isn't good for the gander? Where did I just read this: "Nitpicking isn't going to help the OP."? Unless otherwise stated, nitwit, that the emitter and the source are the terminals to which the base voltage and gate voltage are referenced is implicit.
--- Perfectly clear to me, and for a newbie who has to ask for the difference between a BJT and a FET, an easy way to grasp that a tiny change in base-to-emitter voltage will effect a change in base-to-emitter current which will, in turn, cause a much larger change in collector current.
ISTM that you think beta is so evil that, if you had your way, any mention of beta and all Ic VS Ib curves would be totally eliminated from all the data sheets in the world. It ain't gonna happen, so you might as well get over it.
Or not. It makes very little difference to me, one way or the other.
-- John Fields
But you *do* know it's flawed, don't you - unlike the OP. You've admitted as much to Kevin Aylward. And yet you're still prepared to sell this flawed foundation to the OP!
It's a silly and pointless question so I'll decline, thanks.
[snip]
What a lousy definition. Gate voltage and base voltage as referred to above are totally misleading. The relevant values to concentrate on are Vbe and Vgs; the potential difference applied directly across the base/emitter junction (in the case of the BJT) and the PD applied directly across the gate/source junction in the case of a FET.
Here's what you wrote earlier:
"The problem which arises here, I think, is that the change in base voltage required to affect a change in collector current is so tiny that it becomes easier to consider what happens on the other side of the change in base voltage. That is, the collector-to emitter current change due to the base-to-emitter current change."
Clear enough?
Yes no.
{etc sniped.}
I have no basic problems with this quote, its all good stuff. However, it has absolutely nothing to do with my point. It certainly has no relevance as to why a transistor is a transconductance *device*.
"Transconductance" in the above is a pure and general mathematically technique used to model a physical phenomena. It doesn't care whether or not the phenomena is actually physically current controlled by a voltage. My description that a bipolar is a "transconductance device" is statement of its actual physics.
For a given emitter current, the base current will always be a small fraction due to transistor action. If the npn junction were just a slab of n type then there would be a direct connection from base to emitter resulting in larger current. You would just have resisters connecting base emitter and collector all together and therefore no hfe.
It isnt as far as the base circuit is concerned. It acts as a diode with Ie/hfe
I agree in a loose sense of "seems like", but it just doesn't behave in the same way as a mosfet does in forming a same type channel.
The above statement is with regard to the control of the collector current only. It obviously needs a statement that "base current must exist in real device".
No.
So, what, its still something that ideally, would be zero.
Yes.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
-- Not yes no
-- What you're _really_ afraid of is that you'll be shown up for the disingenuous piece of shit you really are, so you just keep on adding fuel to the fire, buying time, waiting for what you think will be an opportune moment to attack and "vindicate" yourself. Keep it up as long as you like, I don't mind grinding you into the ground at all.
-- _My_ definition? Show me.
-- Believe it!-)
-- Ok, now I see. Your reading comprehension is so poor that you try to excuse yourself by casting the blame for your ignorance on someone else.
-- Yup, I usually hang out with the pelagic fish, but this time I thought I'd come up to the shallows and see what the guppies are doing. What a surprise, there you were in a school of them!
It's not nitpicking, it's vitally important. Vb and Vbe are two different things. Your "definition" should have referred to Vbe. Similarly inexcusably sloppy was the reference to Vgs as Vg.
So all my old textbooks that specifically refer to Vbe and Vgs are being unnecessarily pedantic, then? How are you then going to refer to the 'absolute' values of gate voltage and base voltage (WRT ground) without causing much confusion?? Tell me how a newbie such as the OP or anyone else reading this group to learn about the subject is supposed to *know* that sometimes some idiots write Vg and Vb when they mean Vgs and Vbe? And personal insults are completely pointless, knob-head.
That's the essence of the problem with your approach: easyness. Short cuts are all very well provided they don't subvert fundamental understanding along the way. Your 'easy' solution doesn't cut it in this respect, I'm afraid.
I think you owe the OP one further explanation since you've sought to rely on your 'easy' way out. Kindly explain to him how, if he uses a transistor with a beta listed as say 250 that he may in practice find that his ratio of collector current to base current may be as much as
900:1?
-- Since you obviously don't understand the analogy and are more concerned with 'i' dotting and 't' crossing than you are with anything technically interesting, I can't see what possible difference it would make whether it accurately reflected reality or not. Either way, it would be gobbledegook to you.
No. I have to say here, this is absolute nonsense. I cant believe I am actually reading this.
The concept of transconductance is completely independent of whether or not there is any control current.
Sorry, mate, this is only *your* personal concept of a "true transconductance" device. Somewhere you have picked up an erroneous view without even thinking about it. The *only* requirement for a transconductance is the output current is a direct function of a control voltage. Any current at the control terminal is simply irrelevant.
No it don't. This is getting daft. The bipolar transistor is, to first order, a voltage controlled current source. It is therefore a transconductance device. Period.
Ho hummm...
That's what I am claiming, you are claiming otherwise.
Therefore you are claiming by this that it *is* a slab of resistance.
It is, if we neglect rbb'. The fact that a source has to supply current is irrelevant.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
The definition you sought to rely on is *your* definition - de facto.
Yes, absolutely! It is often said that "a little knowledge is a dangerous thing" and this is where that truism is most apparent; when hobbyists like you get out of their depth and try to 'help' other hobbyists - as we have seen here - and simply end up making yourselves look stupid. You should be more diligent in how you study those 'pedantic' books. Considered entry-level evening classes?
It's crass to expect someone who knows even less about electronics than you do to *know* that.
All the time boneheads like you keep peddling their snake oil, yes.
You're simply not capable. I'm a professional electronics engineer of some 35 years experience. You, OTOH, strike me as someone who has yet to build their first crystal set. You're out of your depth and out of your class, pal.
[snip about datasheets]Listen, bonehead. *You* are the one who brought up the 'easy' solution of Beta, so you explain to the OP how it so often falls apart in practice. I never cited it, okay?? Sheesh!!!
ROTFLMAO!!! Hey, boner, I hope this is simply some crappy analogy you've devised here and not directly quoted from the kind of textbooks you've been studying! BWAHAHAHAHAHAHAHAAAAA!!!
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