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Now, be honest. Did you ever look in to these equations when designing a transistor circuit?
Arouse1973
Adam
Blast from the past lol
True, also never looked at field theory in dielectrics or the chemical makeup
of package plastic or.....
That of course does not negate the legitimacy of models derived from physical principles.
But maybe we should ask the analog designers doing 20+ bit design, heck even 12 bit
over T and V, to see if they care about more precise models.
That being said as a test engineer we looked extensively into modeling
substrate effects to enable heating up parts for test versus ye old environmental
chambers. Even aluminum bond wire mechanical effects.
Its all good.
Regards, Dana.
Of course not.
My quibble it bringing the solid-state semiconductor theory and equations into a discussion with neophytes that may barely understand Ohm's law (and sometimes don't even know that).
Just as we don't need to bring up the field theory of dielectrics when discussing electrical insulators, or the chemical makeup of the plastics used in electronics, or EM theory when designing DC or low frequency AC circuits.
If they ask about the theory, that's a different situation.
It's a matter of knowing your audience.
hevans1944
Hop - AC8NS
Yeah. Everybody that posts a question here should first demonstrate a working knowledge of Ohm's Law, which states that the current in a circuit is proportional to the voltage that created the current and inversely proportional to the resistance in the circuit through which the current occurred. Note that this is an empirical observation derived from experiments involving conductors to which a known voltage is applied and a resulting current measured. I learned this functional relationship, E=IR, as an expression of Ohm's Law. I=E/R is also a valid relationship, as is R=E/I. None of these three relations implies causality, which is a whole different subject.
It is a FACT that Ohm's Law is "only" an experimental (empirical) observation. It is a FACT that Ohm's Law is NOT obeyed by every substance that conducts electricity, even though said (unidentified) substance is by definition a conductor. Nevertheless, I use Ohm's Law (and other "laws") to successfully analyze, explain, and build useful circuits. Newbies should learn how to use Ohm's Law. In the mean time, ask questions There are no dumb questions, but there are plenty of dumb answers. Your job as a newbie is to learn what the dumb answers are so as to avoid them.
That FACT that Ohm's Law does not always apply should not be a deterrent to using Ohm's Law to analyze circuits. As the newbie acquires knowledge and experience they gradually become nerds. They may even gravitate towards nerd jobs and become electronics technicians or electrical engineers or PhDs. Having a PhD is a plus toward obtaining a job as a teacher, instructor, or college professor. However, do not be discouraged by folks who say, "Those that do are distinguished from those that don't because the latter are teachers." I have been taught over the years by plenty of teachers that are also doers... the finest kind of teacher, IMHO.
As @crutschow said, "It's a matter of knowing your audience."
P.S. Thanks to Martin and Adam for finding that old thread!
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I don't know, do not see any direct field theory equations posted. But Ebers-Moll, in virtually all
EE textbooks.....says the current dumb down current operating model, has limitations worthy of
discussion. Not to offend there is the Gummel Poon we all use in Spice sims. Which degenerates
to Ebers Moll under certain conditions.
But I agree, we should move this off ops post, but for curious minds let them know where it
is going to be continued. Assuming OP characteristics is not a useful in "knowing your audience".
Here he did seem to indicate he is new to the field. But I have a weakness for treating people
as experienced and then, based on disclosure, moving to commentary appropriate to accommi-
date the disclosed (not assumed) capability of OP. I also have a trigger, as I believe other senior
helpers here have shown repeatedly, for in-accuracies, to not correct. This clearly makes the
profession robust, trustworthy, safe, and effective.
Regards, Dana.
hevans1944
Hop - AC8NS
Yes, the discipline required for success in almost any endeavor (including the practical applications of electricity and electronics) relies on the practitioner, and his or her knowledge of working theory being robust, trustworthy, safe, and effective. This forum does promote those four desirable qualities, among others. I have tried to abide and embrace them during a fairly long career, first as a hobbyist/experimenter in the 1950s, later as an accomplished electronics technician in the 1960s, and later still as a degreed electrical engineer (BEE, 1978, University of Dayton).
It has been a fun ride so far, and hopefully it isn't over yet! Dana (@danadak) is relatively new here, but I can tell from his posts that he enjoys the profession. To me, that is one of the characteristics required of a great engineer, not just being someone who "wanders in" to the field. I have known plenty of "engineers" who spent four or more years earning their "ticket" but lacked the passion that great engineers acquire. Some of them gave up engineering, for whatever reason, but I always tried to share some of my passion with them before they departed.
My "hero" was Bob Pease (deceased) who was famous for explaining things using a ball-point pen and a paper napkin, or the back of an envelope. He was also quite "messy" in his work environment, which really endeared him to me.
The device may very well go away as a short lived light emitting device. Most likely, emitted light may be too low frequency to be visible to human eye. A short trail of grey smoke would indicate that all emissions have ceased.If you understand what happens when you put 5V in the forward direction across a silicon junction diode, then you will know what happens when you apply 5V to the transistor base-emitter junction in the forward direction.
I think I agree. When plotting beta curves, generally Ice is plotted against Ibe. I propose that Vbe could be 5 volts or 50 volts but if current is limited from emitter to base, Ic will behave according to specs.
Been awhile. I thot hFE was ac gain and beta was DC gain. Not so?
I may have to beg some forgiveness due to a misunderstanding I may have. Personally I define saturation as the state of being "swamped." Saturation to me means that the physical limits of a material has been reached and its ability to absorb, conduct, vibrate with any greater amplitude, etc., is not possible. I may be saying the same thing as crutschow but in a different dialect. For me to consider a BJT to be in saturation, the silicon crystal will be incapable of passing any greater amount of current carries than it is passing at present. ICBM (I Could Be Mistaken ), but consider a saturable reactor. A reactor acts as a variable transformer. As the ac element is passed thru the primary winding, voltage is induced in the secondary winding. If, in a third winding, a dc element is introduced, the resulting static flux of the dc winding is considered in saturation when all power transfer from primary to secondary winding is pinched off even tho the same ac current is applied to the primary. The immediate involved area has been saturated with magnetic flux and by the nature of the reactor's construction, the primary winding cannot add or subtract magnetic flux to its usual working area and transformer action is impossible. The reactor is considered fully OFF when it is in saturation. If a transistor could go into saturation in a real sense, there would be no emitter/collector voltage drop. I believe saturation is a good term to use when a BJT device reaches a point where it in no way could conduct any harder. Excuse me but I have forgotten why I started this explanation. I'll get back to you later.
I'm unclear to the implication of your statement. Hobbyists would be using proven technologies accepted as convention whereas research seems to search for solutions often based on abstract and theoretical notions. Regardless, views and ideas and information can surely be exchanged between these two groups. JMO of course.I think it would depend on whether one considers this as a forum of the Hobby'st or Research'ers
Yes, the discipline required for success in almost any endeavor (including the practical applications of electricity and electronics) relies on the practitioner, and his or her knowledge of working theory being robust, trustworthy, safe, and effective. This forum does promote those four desirable qualities, among others. I have tried to abide and embrace them during a fairly long career, first as a hobbyist/experimenter in the 1950s, later as an accomplished electronics technician in the 1960s, and later still as a degreed electrical engineer (BEE, 1978, University of Dayton).
It has been a fun ride so far, and hopefully it isn't over yet! Dana (@danadak) is relatively new here, but I can tell from his posts that he enjoys the profession. To me, that is one of the characteristics required of a great engineer, not just being someone who "wanders in" to the field. I have known plenty of "engineers" who spent four or more years earning their "ticket" but lacked the passion that great engineers acquire. Some of them gave up engineering, for whatever reason, but I always tried to share some of my passion with them before they departed.
My "hero" was Bob Pease (deceased) who was famous for explaining things using a ball-point pen and a paper napkin, or the back of an envelope. He was also quite "messy" in his work environment, which really endeared him to me.
I was fortunate enough to sit 2 - 3 desks away from Pease for several years. He was a first class "seeker".
I talked to him subsequently more often when I became FAE in Boston than when I sat close to him, his
attendance at seminars.
My boss, Jim Moyer, was good friends with Barry Siegal, manager of Hybrid group doing all the precision
stuff, had many lunches together where I listened. Moyer was also good friends of Both Pease and Jim
Williams (anti computer, LaPlace). Both not fans of models. Whereas my background was CPU starting
1972 in school, and Mainframe and Mini, LaPlace analysis. Loved the idea before one built something
you could "predict" the outcome. Of course none of us was completely right. Models have limitations,
rejection of computers for design work has limitations, but the vigor of the arguments always with the
sole purpose of un-corrupted knowledge seeking. Used to lunch on the National quad daily with many
talented engineers, discussing engineering, innovation, ideas. Great environment which I am sure most
engineers have in one form or another. Its all good. Moyer was also good friends with Dale Mrazek, inventor
TriState. Attended lunches where key discussion was would Dales efforts pushing 2900 Bipolar Bit Slice
would prevail over MOS, guess we know answer to that. His bit slice did find many sockets at the time.
Both Pease and Williams masters of lab work and measurement. Their rich source, still current, of Lab Notes
and app notes excellent reading.
Regards, Dana.
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That's not what "saturation" means for a BJT.
It just means the transistor is fully on where the Vce is less than Vbe, and can occur at any collector current.
It has nothing to do with the transistor limits.
Interestingly, saturation has a different meaning for FETs (just to confuse us).
A FET is saturated when, for a given Vgs, the increase in drain current does not increase significantly with an increase in drain voltage.
That also has nothing to do with limits.
Thats not true. From Sze, 3'rd edition, semiconductor physics, the drift velocity reaches
a saturated value, for which the current density is dependent on, hence also saturates.
Saturation current become drift dominated when CB becomes forward biased.
Regards, Dana.
What's not true in what I said?
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