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Old 12th January 2010, 07:33 PM   #681
Bigun is online now Bigun  Canada
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Originally Posted by Lumba Ogir View Post
I use feedback and it punishes me mercilessly too,
your pain explains the strange posts of yours
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Old 12th January 2010, 08:16 PM   #682
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Lumba has to do professionally with "Heisenberg uncertainty principle"?
No he has quite to do with Sokal's mock. As mocked of course.

Piercarlo
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Old 13th January 2010, 05:40 AM   #683
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SQLGuy,
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This is another ridiculous statement. Heisenberg uncertainty and Planck values describe the minimum of what can be measured in the universe. Period.
It would be exceedingly distressing to use a period denoting full stop after that confused statement. More relevantly, it states that two variables cannot be calculated simultaneously (anywhere in the universe). What to expect from an analysis where linearity and time are mathematical constants and highly influential parameters have ideal values?
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Old 13th January 2010, 10:01 AM   #684
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Quiz: Which is faster?
a) BJT with fT=10MHz and beta=100
b) BJT with fT=10MHz and beta=10
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Old 13th January 2010, 12:13 PM   #685
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Originally Posted by traderbam View Post
Quiz: Which is faster?
a) BJT with fT=10MHz and beta=100
b) BJT with fT=10MHz and beta=10
I choose b), and that's my final answer.
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Old 13th January 2010, 12:23 PM   #686
orjan is offline orjan  Sweden
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Originally Posted by Lumba Ogir View Post
SQLGuy,

linearity and time are mathematical constants
Could you explain a bit more about time and linearity being a constants.

/örjan
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Old 13th January 2010, 12:55 PM   #687
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Originally Posted by traderbam View Post
Quiz: Which is faster?
a) BJT with fT=10MHz and beta=100
b) BJT with fT=10MHz and beta=10
None. Both lack proper propulsion means so they will be having a hard time getting any speed whatsovever.

Seriously, "faster" isn't well defined enough to make much sense. The beta=10 sure has a higher turnover frequency, but the beta=100 has higer or equal current gain at all frequencies. It depends on the application.
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Old 13th January 2010, 01:11 PM   #688
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Howdy,
funny question. Which is higher 10MHz or 10MHz?
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Old 13th January 2010, 01:48 PM   #689
SQLGuy is offline SQLGuy  United States
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Quote:
Originally Posted by Lumba Ogir View Post
SQLGuy,

It would be exceedingly distressing to use a period denoting full stop after that confused statement. More relevantly, it states that two variables cannot be calculated simultaneously (anywhere in the universe). What to expect from an analysis where linearity and time are mathematical constants and highly influential parameters have ideal values?
Sorry. It's called emphasis. It's something we do in English. I didn't realize it would be confusing.

You misunderstand what Heisenberg's principle says. It says that, due to the effects of measurement, e.g. the bombardment of electrons that it would take to illuminate and measure the position of a particle, the very act of measurement disturbs the item being measured. More specifically, it states that you cannot know with pefect precision BOTH the position and velocity of a very small particle. You can know one or the other, but not both. As you increase the precision of one measurement, you reduce the precision of the other.

However, this principle doesn't just define the limits of what can be measured; as far a current modern physics can tell, it defines the limits of what actually exists. In other words, unobserved quantum particles, like electrons, are not point objects, but smears of probability. When observed, the electron will collapse to some point within the space defined by the Schroedinger probability equation. It will probably show up at the point of highest probability, but it could show up anywhere within the "smear." This is how tunneling works. In a tunnel diode, for instance, there is an insulating layer through which electrons cannot pass; but, since the probability fields of the electrons extend beyond this barrier (probability field shapes are not at all influenced by external objects or pressures), some electrons will appear on the other side of the barrier.

The biggest thing to keep in mind, and that I think you are missing, is that this all applies only to VERY SMALL things or VERY SHORT periods of time. Planck discovered and calculated the applications of Heisenberg's principle to define the minimums of things that could be measured. A Planck length, for example, the minimum length that can be measured, is 1.616252×10−35 meters.

Please explain, now, how any of this is going to affect any of LTSpice's very macro analyses.

Thanks,
Paul

Last edited by SQLGuy; 13th January 2010 at 01:52 PM. Reason: typo
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Old 13th January 2010, 03:03 PM   #690
syn08 is offline syn08  Canada
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Quote:
Originally Posted by traderbam View Post
Quiz: Which is faster?
a) BJT with fT=10MHz and beta=100
b) BJT with fT=10MHz and beta=10
If that helps, alpha=1-Tr/Tn where Tr is the transit time through the base and Tn is the minority carrier lifetime in the quasineutral base. Recall beta = alpha/(1-alpha) and, of course, low Tr means high Ft.

Now you draw the conclusion. Whatever that is, I'll tell you in advance it's wrong for at least two good reasons:

- The base concentration grading is essential for defining Tr. As such, this is way more important than the simple Tr to alpha relationship, and can easily reverse the conclusion.

- While Ft is a small signal related number, where the device models are already linearized, "speed" is usually related to the large signal model where the nonlinear charge injection and transport mechanisms are dominant.

Comparing Ft with the "speed" and correlating to beta is at best as correct as comparing small signal and large signal slew rates in an amp. A relationship may exist, but it doesn't always hold for all topologies and is ultimately largely irrelevant.
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