an electronish puzzle

[Larry Brasfield]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message news:fki841lkr811i9f64nsk0qqtepvhaoh7kc@4ax.com...

On Fri, 25 Mar 2005 09:13:28 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:
....
Here is what I think the setup will look like:
___
.------|___|------.
| |
| * || |
o-------------||--o
| || |
| |\| |
o--------|-\ |
| | >-----'
| +3V-|+/
GND DUT | |/|
DC source | |/
/ \ GND-|
( ~ ) |> * = HF stabilization only
\_/ |
GND | ___ |
| '----|___|---o
/ \ |
( ~ ) ---
\_/ Sig gen ---
| ___ |
'----------|___|---'

Constructive comments are welcome.

Are you going to measure it, or talk it to death? I could have done it
in 10 minutes, about twice what it took to do the DC version.

I'm going to get my sig-gen back from a friend,
get a current (and paying) mini-project cleared
off my limited workspace, and measure it as I've
shown. It could be a few days or a week. Is
that going to cause any real problems here?

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Jim Thompson]

On Wed, 23 Mar 2005 08:51:01 -0800, John Larkin
<jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

On Wed, 23 Mar 2005 09:02:16 -0700, Jim Thompson
thegreatone@example.com> wrote:

On Wed, 23 Mar 2005 08:00:25 -0800, John Larkin
jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

On Wed, 23 Mar 2005 08:02:13 GMT, Fred Bloggs <nospam@nospam.com
wrote:

There is more of your narcissism- like who cares what you do or do not
respect. And I don't know why you would have any respect for me- I
certainly have none for you- this should be clear to you by now- what's
there about you to respect or even be interested in.

Ah, but then you haven't seen my collection of colorful little
earthenware coffee pots.

John

Knock it off, John! You have me laughing so much my stomach hurts ;-)

...Jim Thompson


What, do you think I would joke, JOKE about my pots? As if!

See abse, and try to show some respect.

John

I didn't doubt that you had the pots. I was just laughing at the
smooth retort.

Me, I collect Native American art.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[John Larkin]

On Fri, 25 Mar 2005 10:04:41 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message news:fki841lkr811i9f64nsk0qqtepvhaoh7kc@4ax.com...
On Fri, 25 Mar 2005 09:13:28 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:
...
Here is what I think the setup will look like:
___
.------|___|------.
| |
| * || |
o-------------||--o
| || |
| |\| |
o--------|-\ |
| | >-----'
| +3V-|+/
GND DUT | |/|
DC source | |/
/ \ GND-|
( ~ ) |> * = HF stabilization only
\_/ |
GND | ___ |
| '----|___|---o
/ \ |
( ~ ) ---
\_/ Sig gen ---
| ___ |
'----------|___|---'

Constructive comments are welcome.

Are you going to measure it, or talk it to death? I could have done it
in 10 minutes, about twice what it took to do the DC version.

I'm going to get my sig-gen back from a friend,
get a current (and paying) mini-project cleared
off my limited workspace, and measure it as I've
shown. It could be a few days or a week. Is
that going to cause any real problems here?

Since I don't expect that you will find the thermal effect, and
because the point is entirely academic anyhow, no problems.

John

 

[Ken Smith]

In article <n03741djgnh09ndj0p7dapvttlu1g1n4tk@4ax.com>,
John Larkin <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:
[...]

If you do it this way, the spike from charging the C-E capacitance will be
something like 8V. This means the full scale of the scope must be about
20 times the signal to be measured. This is losing you the top 4 bits of
the number.


But the transition from zero emitter current to lots of current will
happen in 0.1 volts delta Vbe or less. And the base is an ideal shield
between the emitter and the collector, which is why people like
cascodes (hell, you could *do* it as a cascode.)

Yes, you've got me there. You could preposition the emitter voltage at
just below its breakdown.

This *is* starting to sound easier than stablizing the temperature.

--
--
kensmith@rahul.net forging knowledge

 

[Ken Smith]

In article <UEX0e.12$aL5.311@news.uswest.net>,
Larry Brasfield <donotspam_larry_brasfield@hotmail.com> wrote:

"Ken Smith" <kensmith@green.rahul.net> wrote in
[...]
How are you going to deal with the non-linearities of the capacitances and
the fact that they don't have a zero damping factor?

Can you elaborate on that? (maybe after considering
the discussion on non-linearity as developed below)
The "damping factor" issue completely escapes me.

The transistor really looks like this:


----+----/\/\/----!!-------+------
! !
+--/\/\/-- --/\/\--+
! \ / !
\ ----- /
/ ! \
\ / /
! \ !
--- / ---
--- \ ---
! ! !
-----------+----------
!

As a result none of the capacitive effects will truely be at 90 degrees
and the emitter current of the ideal device will actually lag the current
you drive into the emitter lead.

[...]

It seems to me that it allows better separation of the
confounding variables, at least the ones I know of.
Which variables do you believe are more confounding
with single frequency excitation? (Mind you, I am
not saying only one frequency is to be used in the
experiment -- just that they are used one at a time.)

From your earlier post I got the impression that you intended to use a
single frequency. If you use a wide enough range of frequencies, the
various confounding factors such as the emitter base capacitance can be
estimated and removed from the results.

[...]

What will happen to the capacitance of the E-B juntion as the zener
current changes?

I don't think it is sensitive to current per-se. To get
that current change, the voltage must change. And
that modulates the depletion region width, which of
course is as non-linear as the doping profile is non-
constant (away from the junction itself).

When you change the carrier density, the optical refractive index of a
semiconductor changes. Passing a current through a junction causes the
speed of light within that hunk of semiconductor to decrease. This is
because the dielectric constant of the semiconductor is effected by the
carriers in it. I don't see any basis on which you can assume that the
emitter capacitance will not change with the zener current.

I agree that non-linearity can be a real complication.
But its impact can be reduced by using the AC
excitation approach, with signals made small enough.

How small do you have to make them to make the non-linearities a
corrupting factor in the experiment?

[...]

Here is what I think the setup will look like:
___
.------|___|------.
| |
| * || |
o-------------||--o
| || |
| |\| |
o--------|-\ |
| | >-----'
| +3V-|+/
GND DUT | |/|
DC source | |/
/ \ GND-|
( ~ ) |> * = HF stabilization only
\_/ |
GND | ___ |
| '----|___|---o
/ \ |
( ~ ) ---
\_/ Sig gen ---
| ___ |
'----------|___|---'

Constructive comments are welcome.

Use a generator with offset and amplitude controls and simplify the
emitter circuit.

--
--
kensmith@rahul.net forging knowledge

 

[Ken Smith]

In article <lg4741hdpsfu732iej83htr6q1snjtaaf9@4ax.com>,
John Larkin <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:
[...]

50 MHz, using a 1008 surface-mount coil with a ceramic body. The boys
have just about got me convinced to use an SPI temp sensor, some math
in the uP, a DAC, and a varicap to zap the tempco. Given how much
trouble I'm having getting NTC caps, I suppose they're right, grumble.
Brute force wins again.

Cygnal makes micros that can measure there own temperature.

--
--
kensmith@rahul.net forging knowledge

 

[John Larkin]

On Fri, 25 Mar 2005 22:28:07 +0000 (UTC), kensmith@green.rahul.net
(Ken Smith) wrote:

In article <UEX0e.12$aL5.311@news.uswest.net>,
Larry Brasfield <donotspam_larry_brasfield@hotmail.com> wrote:
"Ken Smith" <kensmith@green.rahul.net> wrote in
[...]
How are you going to deal with the non-linearities of the capacitances and
the fact that they don't have a zero damping factor?

Can you elaborate on that? (maybe after considering
the discussion on non-linearity as developed below)
The "damping factor" issue completely escapes me.


The transistor really looks like this:


----+----/\/\/----!!-------+------
! !
+--/\/\/-- --/\/\--+
! \ / !
\ ----- /
/ ! \
\ / /
! \ !
--- / ---
--- \ ---
! ! !
-----------+----------
!

As a result none of the capacitive effects will truely be at 90 degrees
and the emitter current of the ideal device will actually lag the current
you drive into the emitter lead.

[...]
It seems to me that it allows better separation of the
confounding variables, at least the ones I know of.
Which variables do you believe are more confounding
with single frequency excitation? (Mind you, I am
not saying only one frequency is to be used in the
experiment -- just that they are used one at a time.)

From your earlier post I got the impression that you intended to use a
single frequency. If you use a wide enough range of frequencies, the
various confounding factors such as the emitter base capacitance can be
estimated and removed from the results.

[...]
What will happen to the capacitance of the E-B juntion as the zener
current changes?

I don't think it is sensitive to current per-se. To get
that current change, the voltage must change. And
that modulates the depletion region width, which of
course is as non-linear as the doping profile is non-
constant (away from the junction itself).

When you change the carrier density, the optical refractive index of a
semiconductor changes. Passing a current through a junction causes the
speed of light within that hunk of semiconductor to decrease. This is
because the dielectric constant of the semiconductor is effected by the
carriers in it. I don't see any basis on which you can assume that the
emitter capacitance will not change with the zener current.


I agree that non-linearity can be a real complication.
But its impact can be reduced by using the AC
excitation approach, with signals made small enough.

How small do you have to make them to make the non-linearities a
corrupting factor in the experiment?

[...]
Here is what I think the setup will look like:
___
.------|___|------.
| |
| * || |
o-------------||--o
| || |
| |\| |
o--------|-\ |
| | >-----'
| +3V-|+/
GND DUT | |/|
DC source | |/
/ \ GND-|
( ~ ) |> * = HF stabilization only
\_/ |
GND | ___ |
| '----|___|---o
/ \ |
( ~ ) ---
\_/ Sig gen ---
| ___ |
'----------|___|---'

Constructive comments are welcome.

Use a generator with offset and amplitude controls and simplify the
emitter circuit.

This thread is getting funnier and funnier.

You guys are hilarious. Thanks.

John

 

[John Larkin]

On Tue, 22 Mar 2005 10:04:59 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote
in message news:lkm041dujd0erjhiok06jv0jk9jt6fkue2@4ax.com...
On Tue, 22 Mar 2005 08:07:49 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:aoe0411sep2qt5mcomjjel04u5lgslrmbg@4ax.com...
[SNIP]
, why don't you do
your own legwork and report back with what you find?

I plan to do just that, presuming you mean variations on the
experiment reported by John Larkin. AC b-e current is
sure to separate thermal effects from the other effects.

Well, you are implying that I can't tell a straight line from an
exponential. That's not very nice, you know.


I was not trying to say that. I'm sure there is a
thermal effect, and I intend to see the others
(such as you appear to have reported) without
the confusion of a superimposed exponential.

OK, but you're going to have to resolve nanoamps in milliseconds.
Sounds like a project.

John

 

[Terry Given]

John Larkin wrote:

On Tue, 22 Mar 2005 09:13:25 -0600, John Fields
jfields@austininstruments.com> wrote:


On Mon, 21 Mar 2005 16:24:58 -0800, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:


On Mon, 21 Mar 2005 15:39:06 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:



You wrote earlier:
It's apparently linear up to Ie of 10 mA, all i did,
at which time Ic is up to 260 nA.
If it was not exponential, as the temperature effect
would cause, then either your transistor is going
into avalanche or the mechanism at work is one
which has eluded everybody here (who played),
including myself, along with a number of bright
interviewees including one with a PhD obtained
after his work in novel semiconductor devices.
I will soon be asking him again about this puzzle.
For all I know, there could be another, parallel
effect in addition to all the tunneling.



I'm an engineer, so when theory collides with parts, I trust the
parts.


"One experiment is worth a thousand expert opinions."

- Werner Von Braun.


---
Fred Bloggs wrote:

In the case of the OP292 thread, the motivation was to make a dead
certain diagnosis of the Nazi Clarence and his problem- and that is
what I did- also ordered some OP292's and played around with it some
more.
...


John Larkin wrote:

You actually ordered parts and built circuits to prove somebody from a
newsgroup to be wrong? That's pushing the top range of the
getalifeometer!

...


If you believe what you quoted:, "One experiment is worth a thousand
expert opinions.", then buying or building parts to prove a point in
the real world isn't something which should be ridiculed, it's
something which should be respected. After all, spending
discretionary income just to prove a point with no hope of
remuneration or, God forbid, gain, rocks. That is, it proves
committment to an ideal.



The "ideal", in his case, is to prove other people stupid in cases
where ordinary insults and obscenities aren't enough.

If Fred had a legitimate need, or just intellectual curiosity, about
this issue, then that has my respect; so why doesn't he share it with
us?

If he did it to prove that someone is an idiot, then he's running true
to form.


I seem to recall that you said that as a result of experimentation on
some of your stuff you're now shipping equipment with "oscilloscope
simulators" installed which, without, equipment you're selling won't
work properly.


The "oscilloscope simulators" part doesn't sound familiar to me.


You also said that you didn't understand just why it
made the equipment work, so that seems to me to be a good example of
experiment taking the place of theory.


Can't recall that. Got a reference?

Oh, do you mean the cap on the Xilinx pin? That's hardly an
oscilloscope simulator! It's zapping some ringing or something. You
might note that I shared that observation with the OP in the hopes of
helping him with a similar problem, and did *not* insult him or call
him an idiot.

Theory is only useful if it's predictive; even the scientists agree on
that. I just finished reading Dahl's book, "Flash of the Cathode
Rays", which is all about this. Surprisingly good, fun to read book,
given that it's about the history of subatomic particles. The parts
about N-rays and sub-e charges are especially cool.

Is it true about the american physicist (IIRC) pocketing a vital piece
of apparatus during a demonstration, not affecting the outcome and
thereby blowing N-rays out of existence?

I might have to read that book.

Cheers
Terry

[snip cos I DGAS]