🚀 go-pugleaf

In article <368F5F2C.3BF0@armory.com>,
	Richard Steven Walz <rstevew@armory.com> writes:
> Duncan Barclay wrote:
>> 
>> In article <76kgnq$lin$1@news-1.news.gte.net>,
>>         Doug <do@not.spam> writes:
>> > Duncan Barclay wrote:
>> >> A BJT allows you to control a current by varying the base emitter
>> >> voltage.
>> >
>> > Your claim that the BJT is also a voltage controlled device
>> > does work as a model.  No one is denying that.  But, the
>> > effect of the voltage on the BJT is to allow current
>> > injection to occur.
>> 
>> Precisely,
>>   1) VBE voltage controls current injection at BE juntion
>>   2) current injection at the BE junction controls collector current
>> 
>> Cause and effect....
>> 
>> > In other words, your voltage source must include current.
>> 
>> Can't parse that, by definition a voltage source can supply an infinite
>> ammount of current, but it does not include it.
>---------------------------------------------------
> If you can't parse that you need a new parser!!  If you put a cap in
> the base feed, then the transistor doesn't work no matter the
> voltage the base feels, now, does it?


At DC corrent.  Any JFET will fail too.  You still need to support the
leakage current.  This can be supported by other leakage paths. 
MOSFETs will be okay as long as the right ammount of charge is added
to the gate. AC/pulse circuits different matter, have a look at some
Class C RF power amplifiers.

> This is the difference!!  The
> FET will work, the BJT won't!!  You're being quite silly and
> pig-headed about this, and it makes me wonder if this wasn't an
> ill-addressed "hole" in your education that is only showing-up now
> at this late date.  Then perhaps you partied through solid state?

Nope, no holes in my education.  Being taught transistors by one of
the leading UK researchers into BJTs when they were first invented
(Prof.  Greville Bloodworth).  Him allowing me to teach his
undergrads.  Designing "right first time" silicon for a GSM single
chip transeiver IC, "right first time" silicon for a 2GHz proof of
concept RFIC, GaAs ICs galore (not all right first time though). 
D.Phil in circuit design and device modelling including development of
a HEMT model.

>-Steve
> 
>> > Under the assumption that the BJT is ONLY a voltage device is to say
>> > that under a perfect model of a BJT, no current injection is the
>> > desired state.  It is not.  Last I saw, BOTH the EM and GP models
>> > have current injection forms.  Gee, I wonder why ...
>> 
>> To get fundemental, all active devices are voltage controlled because
>> nature does not provide a current source (no monopoles). BJTs, valves,
>> FETs are all govered by electrostatic fields. Remember Schrodinger's
>> Equation, or band bending or Laplace's Law or the Boltzmann Transport
>> Equation? All the eqautions are of the form
>> 
>>   [charge_ammount, charge_momentum, charge position] = f(electric
>field)
>> 
>> Duncan
>-------------------------------
>Yes, yes, physics again. I came that way as well, but if you UNDERSTAND
>QM and uncertainty then you kNOW the fallacy of cause and effect!!
>Especially in electronics!! You wish to:
>1) Assert that all current flows BECAUSE of voltage, heuristically
>useful but not provable. 

Useful proof for electronics:
  Current = movement of charge.

  Charges move under the influence of an externally applied force.

  Most useful force in electronics is a EM field.

  EM fields can only exists if an electric potential exists.  As 
  there are no magnetic monopoles (a dipole has an assiociated
  electic field).

Pedantic hole in proof:
  What about just picking a bucket of electrons up and walking across
  the room...

>2) You wish to redefine electronic engineering after we have the
>definitions standard at that level, you won't win this one, we call
>things voltage or current-controlled because it is USEFUL to do so,  
>and your way avoids utility with some kind of freshman zeal for
>questioning that misses the point entirely, as do most freshmen!

My statements as to how a BJT works are correct (as other posters
have indicated). You seem to think I restrict the use of a term like
VCCS to an ideal linear device. I don't. Linearity in electronics is
a useful approximation to reality, I like to understand things at
all levels of approximation.

As I have said, viewing a BJT in some circuits as a CCCS is useful. I
find that analysis/understanding is easier for most circuits as a VCCS
with gm being the most important parameter. This also happens to be
closer to physical device operation than a CCCS.

>We go by the best linearity-driven cause and effect heuristics for
>that one, and you seem to LIKE freshman heuristics, so you really
>should LOVE this one, you're just being stubborn because you were
>caught in an indefensible statement. Come off it!

Duncan

-- 
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Duncan Barclay          | God smiles upon the little children,
dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned.
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