an electronish puzzle

[Larry Brasfield]

Hmmm, a slow day w.r.t. technical stuff.

Here is a question for anybody who claims (or would like
to pretend) expertise in semiconductor physics, and how
semiconductor device operation is explained or predicted.

Suppose you have a BJT of the usual sort, having
a low emitter-base reverse breakdown voltage.
Reverse bias the collector-base junction and put
a current meter in series with the collector. Now,
force a small current, in breakdown mode, thru
the emitter-base junction. What happens to the
current as indicated by the meter? Now, why?

Have fun!

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

 

[Fred Bloggs]

Take your f_cking puzzle and shove it up your ass- this was a famous
Pease Porridge subject and has been covered thoroughly in the NG on
numerous occasions.

Larry Brasfield wrote:

Hmmm, a slow day w.r.t. technical stuff.

Here is a question for anybody who claims (or would like
to pretend) expertise in semiconductor physics, and how
semiconductor device operation is explained or predicted.

Suppose you have a BJT of the usual sort, having
a low emitter-base reverse breakdown voltage.
Reverse bias the collector-base junction and put
a current meter in series with the collector. Now,
force a small current, in breakdown mode, thru
the emitter-base junction. What happens to the
current as indicated by the meter? Now, why?

Have fun!

 

[Genome]

"Larry Brasfield" <donotspam_larry_brasfield@hotmail.com> wrote in message
news:eW1%d.54$te2.755@news.uswest.net...

[DERF]

I'd rather have a wank.

Perhaps I should explain the art of wanking.

Why not fuck off to India and get a job in a call centre. Then you get to
phone strangers direct, ask them stoopid questions, and get told to fuck
off.

Plus you get paid for it.

DNA

PS, it's not a Bloggs thing. You just asked for it.

Try not to type.

 

[Larry Brasfield]

Hmm, looking for an alleged discussion on Google, I come
across this little tidbit on electronish matters. The subject
was "Diode with very low reverse leakage current?" and
came up on January 10 this year. The two quotes below,
demarked with '| ' and '- ' (to reduce quoting confusion),
were lifted from the Google archive via cut-and-paste.

A question arose whether the b-c or b-e junction would have
lower leakage when reverse biased. Somebody had cited
'Bob Pease in "Troubleshooting Analog Circuits" (page 66)'

I replied thusly:
- With all due respect for Mr. Pease, I'm going to stick my
- neck out and disagree. Most of the leakage of a diode comes
- from surface leakage and thermally generated carriers in the
- depletion region. For a normally built BJT, the B-E junction
- has less exposed surface than the B-C junction and also has
- a smaller volume depletion region, being both narrower and
- occupying somewhat less area. So, unless one requires a
- reverse breakdown higher than the several volts available
- from a B-E junction, it is the better choice. (I am willing to
- be proven wrong on this, but it will take some evidence.)
- I suspect Mr. Pease's advice was directed toward the case
- where more than 3 to 6 Volts of reverse standoff is needed.

Some would-be resident expert chimed in:
| Well you know that alpha_F x Ieo = alpha_R x Ico, so that right there
| tells you that Ico is an integer multiple or two of Ieo. Pease is
| *never* wrong, so it must be that the Early effect narrowing of the EB
| depletion region causes that junction reverse saturation current to
| surpass the BC diode leakage in some exponential way with voltages
| smaller than breakdown.

People who were paying attention in their semiconductor
physics classes, or worked at becoming knowlegable,
know that the Early effect occurs because of depletion
width changes alright, but in fact, the effect only applies
to a BJT biased in the traditional active region. It occurs
because, as the b-c junction depletion region widens,
(with increasing voltage), the base region narrows,
reducing recombination losses which, effectively,
increases beta. (With fixed base current, you can think
of it simply as the reduced losses going directly toward
increased collector current.)

The notion, presented with equations and all, that Early
effect even has any meaning when applied to individual
junctions, is patent nonsense and a good example of
the kind of plunge into the unknown I have mentioned.

The same comments apply to the idea that alpha_anything
would apply to individual junctions. As those who know
know, alpha is also related to recombination losses in
a two junction scenario. It does not apply to just one.

I did not even answer then, and neither did anyone else,
so perhaps Fred would like to defend such "expertise"
now. I'm taking bets on the direction this goes.

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:423CADF8.1010802@nospam.com...
[invective and commands cut]

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

 

[Larry Brasfield]

"Genome" <ilike_spam@yahoo.co.uk> wrote in message
news:cR2%d.3763$Kt5.1711@newsfe2-gui.ntli.net...

I'd rather have a wank.

Perhaps I should explain the art of wanking.

Well, I'm sure that you can be the resident expert
in some forum where that would be topical. Need
some help finding it?

[more comedy cut with amusement]
--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[John Larkin]

On Sat, 19 Mar 2005 15:53:25 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

Hmm, looking for an alleged discussion on Google, I come
across this little tidbit on electronish matters. The subject
was "Diode with very low reverse leakage current?" and
came up on January 10 this year. The two quotes below,
demarked with '| ' and '- ' (to reduce quoting confusion),
were lifted from the Google archive via cut-and-paste.

A question arose whether the b-c or b-e junction would have
lower leakage when reverse biased. Somebody had cited
'Bob Pease in "Troubleshooting Analog Circuits" (page 66)'

I replied thusly:
- With all due respect for Mr. Pease, I'm going to stick my
- neck out and disagree. Most of the leakage of a diode comes
- from surface leakage and thermally generated carriers in the
- depletion region. For a normally built BJT, the B-E junction
- has less exposed surface than the B-C junction and also has
- a smaller volume depletion region, being both narrower and
- occupying somewhat less area. So, unless one requires a
- reverse breakdown higher than the several volts available
- from a B-E junction, it is the better choice. (I am willing to
- be proven wrong on this, but it will take some evidence.)
- I suspect Mr. Pease's advice was directed toward the case
- where more than 3 to 6 Volts of reverse standoff is needed.

Some would-be resident expert chimed in:
| Well you know that alpha_F x Ieo = alpha_R x Ico, so that right there
| tells you that Ico is an integer multiple or two of Ieo. Pease is
| *never* wrong, so it must be that the Early effect narrowing of the EB
| depletion region causes that junction reverse saturation current to
| surpass the BC diode leakage in some exponential way with voltages
| smaller than breakdown.

People who were paying attention in their semiconductor
physics classes, or worked at becoming knowlegable,
know that the Early effect occurs because of depletion
width changes alright, but in fact, the effect only applies
to a BJT biased in the traditional active region. It occurs
because, as the b-c junction depletion region widens,
(with increasing voltage), the base region narrows,
reducing recombination losses which, effectively,
increases beta. (With fixed base current, you can think
of it simply as the reduced losses going directly toward
increased collector current.)

The notion, presented with equations and all, that Early
effect even has any meaning when applied to individual
junctions, is patent nonsense and a good example of
the kind of plunge into the unknown I have mentioned.

The same comments apply to the idea that alpha_anything
would apply to individual junctions. As those who know
know, alpha is also related to recombination losses in
a two junction scenario. It does not apply to just one.

I did not even answer then, and neither did anyone else,
so perhaps Fred would like to defend such "expertise"
now. I'm taking bets on the direction this goes.

"Fred Bloggs" <nospam@nospam.com> wrote in message
news:423CADF8.1010802@nospam.com...
[invective and commands cut]

Fred is, incorrectly I think, referring to Pease's puzzle in which
negative c-b *voltage* is measured as a result of zenering the b-e
junction. Pease attributes it to light being generated in the zenered
junction and photovoltaic action in the collector. Your bias situation
is different, although you may be referring to a similar optical
coupling.

Anyway, I'm interested, especially is there is a non-photocoupled
mechanism of carrier transfer when the b-e is zenered. Please explain.

John

 

[Larry Brasfield]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote
in message news:qogp31116bnqlf3pscv777ftb05pcjc5er@4ax.com...

On Sat, 19 Mar 2005 15:53:25 -0800, "Larry Brasfield"
[Diode leakage plunge cut.]
Fred is, incorrectly I think, referring to Pease's puzzle in which
negative c-b *voltage* is measured as a result of zenering the b-e
junction. Pease attributes it to light being generated in the zenered
junction and photovoltaic action in the collector. Your bias situation
is different, although you may be referring to a similar optical
coupling.

I could not find the alleged discussion using words that
would surely arise if "it" had been "covered thoroughly".
("It" being the puzzle I posed as the OP.) But I would
like to see that puzzle. With his cute titles in the online
archive, I could not see anything about b-c zenering.
Do you (anybody else) have some date, link, or title?

Anyway, I'm interested, especially is there is a non-photocoupled
mechanism of carrier transfer when the b-e is zenered. Please explain.

No, to first order. Yes, to higher order effects. I would
like to let the discussion develop somewhat, (at least as
much as it can along rational lines), before justifying that
answer. At that time, I will provide an explanation which
will be cogent and convincing to those who know the
subject matter. If you do not want to participate [1], I
would be happy to email it to you before then. (I do
not have it written yet, so the outline would be first
followed by better writing and supporting argument.)

[1. This is not a "Who's got the cajones?" challenge. It
can be a fun discussion, as I have discovered in half a
dozen interviews with people who made the claim. ]

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

 

[John Larkin]

On Sat, 19 Mar 2005 16:49:34 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

No, to first order. Yes, to higher order effects. I would
like to let the discussion develop somewhat, (at least as
much as it can along rational lines), before justifying that
answer. At that time, I will provide an explanation which
will be cogent and convincing to those who know the
subject matter. If you do not want to participate [1], I
would be happy to email it to you before then. (I do
not have it written yet, so the outline would be first
followed by better writing and supporting argument.)

Oh, I'll just wait. My comprehesion of semiconductor physics is small
and mostly qualitative, which suits me fine: I'm a circuit (not IC)
designer.

But you are being a bit coy, which might annoy some people.


John

 

[Jim Thompson]

On Sat, 19 Mar 2005 17:01:22 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 19 Mar 2005 16:49:34 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:


No, to first order. Yes, to higher order effects. I would
like to let the discussion develop somewhat, (at least as
much as it can along rational lines), before justifying that
answer. At that time, I will provide an explanation which
will be cogent and convincing to those who know the
subject matter. If you do not want to participate [1], I
would be happy to email it to you before then. (I do
not have it written yet, so the outline would be first
followed by better writing and supporting argument.)



Oh, I'll just wait. My comprehesion of semiconductor physics is small
and mostly qualitative, which suits me fine: I'm a circuit (not IC)
designer.

But you are being a bit coy, which might annoy some people.


John

And inexperienced. Anything with leads... leakage becomes totally
unpredictable.

...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.

 

[Larry Brasfield]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com>
wrote in message news:veip311lull6tlemiaajuagt93j74gdki1@4ax.com...

On Sat, 19 Mar 2005 16:49:34 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:

No, to first order. Yes, to higher order effects. I would
like to let the discussion develop somewhat, (at least as
much as it can along rational lines), before justifying that
answer. At that time, I will provide an explanation which
will be cogent and convincing to those who know the
subject matter.
....
But you are being a bit coy, which might annoy some people.

Good point. To forestall that for those susceptible
to reason, I should point out that I have had 27+
years to think about this and the opportunity to
discuss it with some people who really do know
the subject well, including one who had devised
some experimental ICs and new basic devices.
I'm not sure it is quite fair to me to come in as
a regular contender under those circumstances.
And if I meant simply to dump a tutorial, I would
not use the "puzzle" subterfuge.

As I said, it can be a fun discussion. I mean to
let it run that way, not "settle" it with all the noise
that would incite among the resident idiots.

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

 

[John Larkin]

On Sat, 19 Mar 2005 17:20:36 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

I'm not sure it is quite fair to me to come in as
a regular contender under those circumstances.
And if I meant simply to dump a tutorial, I would
not use the "puzzle" subterfuge.

For Pete's sake, tell us or don't. Since no sane person deliberately
zeners b-e junctions on transistors that matter, it's not like it's
important.

John

 

[Fred Bloggs]

Larry Brasfield wrote:

Some would-be resident expert chimed in:

Oh there is no would-be to it- I will be here long after you're dead.

| Well you know that alpha_F x Ieo = alpha_R x Ico, so that right
there | tells you that Ico is an integer multiple or two of Ieo.
Pease is | *never* wrong, so it must be that the Early effect
narrowing of the EB | depletion region causes that junction reverse
saturation current to | surpass the BC diode leakage in some
exponential way with voltages | smaller than breakdown.

People who were paying attention in their semiconductor physics
classes, or worked at becoming knowlegable, know that the Early
effect occurs because of depletion width changes alright, but in
fact, the effect only applies to a BJT biased in the traditional
active region. It occurs because, as the b-c junction depletion
region widens, (with increasing voltage), the base region narrows,
reducing recombination losses which, effectively, increases beta.
(With fixed base current, you can think of it simply as the reduced
losses going directly toward increased collector current.)

The notion, presented with equations and all, that Early effect even
has any meaning when applied to individual junctions, is patent
nonsense and a good example of the kind of plunge into the unknown I
have mentioned.

The same comments apply to the idea that alpha_anything would apply
to individual junctions. As those who know know, alpha is also
related to recombination losses in a two junction scenario. It does
not apply to just one.

I did not even answer then, and neither did anyone else, so perhaps
Fred would like to defend such "expertise" now. I'm taking bets on
the direction this goes.

Hey everybody- read what the pseudo-intellectual and pretentious hot-air
bag Larry Brasfield wrote- and this is the individual who clearly came
on SED to kick ass- explaining basic op amp theory, Miller effect,
logarithmic distributions and lots of other stuff to us morons. This boy
is getting the sh_t kicked out of him repeatedly- apparently the moron
knows nothing about Ebers-Moll and SPICE because forward and reverse
current transfer ratios and forward and reverse Early voltages are used
to account for transistor operation for all combinations of forward and
reverse bias operation- the Early voltages in particular are used to
account for the non-zero conductivity of reverse biased output junctions
that are current controlled. This Brasfield crap about "the effect only
applies to a BJT biased in the traditional active region" is total
horseshit and just plain wrong! Once again the pretentious windbag gets
his ass kicked- but there will be no reaction- he is a psychopathic
narcissist and pompous ass.

 

[richard mullens]

Larry Brasfield wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com
wrote in message news:veip311lull6tlemiaajuagt93j74gdki1@4ax.com...

On Sat, 19 Mar 2005 16:49:34 -0800, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:


No, to first order. Yes, to higher order effects. I would
like to let the discussion develop somewhat, (at least as
much as it can along rational lines), before justifying that
answer. At that time, I will provide an explanation which
will be cogent and convincing to those who know the
subject matter.

...

But you are being a bit coy, which might annoy some people.


Good point. To forestall that for those susceptible
to reason, I should point out that I have had 27+
years to think about this and the opportunity to
discuss it with some people who really do know
the subject well, including one who had devised
some experimental ICs and new basic devices.
I'm not sure it is quite fair to me to come in as
a regular contender under those circumstances.
And if I meant simply to dump a tutorial, I would
not use the "puzzle" subterfuge.

As I said, it can be a fun discussion. I mean to
let it run that way, not "settle" it with all the noise
that would incite among the resident idiots.

Fred is right.
He may not put it very diplomatically, but he is right none the less.

 

[Ken Smith]

In article <64lp31tmppr5e0iqki0s7jf2vsq5jmiofm@4ax.com>,
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
[...]

For Pete's sake, tell us or don't. Since no sane person deliberately
zeners b-e junctions on transistors that matter, it's not like it's
important.

Who are you calling insane!!!!! :>


The pop-tronics surf synthesizer used a back biased E-B junction as the
basic white noise source. It also used 3 free running multivibrators to
make a "random" voltage to feed the variable gain.

Don't try this trick with a Darlington unless you want an only slightly
random saw tooth.

BTW: If you do back bias the collector junction with lets say 20V and
force a moderately large current into the E-B junction, the meter on the
collector circuit twitches up scale just as there is a bright flash and a
loud bang. I think this is due to the pyro-electric effect in the
semiconductor more than from the plasma conduction, but I'm not sure. I
think further experiments are in order.

--
--
kensmith@rahul.net forging knowledge

 

[John Larkin]

On Sun, 20 Mar 2005 02:43:12 +0000 (UTC), kensmith@green.rahul.net
(Ken Smith) wrote:

In article <64lp31tmppr5e0iqki0s7jf2vsq5jmiofm@4ax.com>,
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
[...]
For Pete's sake, tell us or don't. Since no sane person deliberately
zeners b-e junctions on transistors that matter, it's not like it's
important.

Who are you calling insane!!!!! :


The pop-tronics surf synthesizer used a back biased E-B junction as the
basic white noise source. It also used 3 free running multivibrators to
make a "random" voltage to feed the variable gain.

Yeah, that's OK. We used to use transistors as reference zeners: take
an NPN, leave the base open, and use c:e as a 6.2 volt zener. For some
transistors, the forward-biased b-c junction temperature compensates
the b-e zener very nicely. Nowadays, it's safer to just buy a
reference IC.

But zenering a transistor does permanently damage to beta, so once
it's a zener, it's always a zener.

Does anybody know how much zenering (in coulombs or whatever) it takes
to hurt a common small-sig transistor?

Don't try this trick with a Darlington unless you want an only slightly
random saw tooth.

BTW: If you do back bias the collector junction with lets say 20V and
force a moderately large current into the E-B junction, the meter on the
collector circuit twitches up scale just as there is a bright flash and a
loud bang. I think this is due to the pyro-electric effect in the
semiconductor more than from the plasma conduction, but I'm not sure. I
think further experiments are in order.

And some people claim that indirect-bandgap semiconductors won't emitt
light!

John

 

[Larry Brasfield]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com>
wrote in message news:64lp31tmppr5e0iqki0s7jf2vsq5jmiofm@4ax.com...

For Pete's sake, tell us or don't.

Alright. Since nobody got interested in this, I'll keep
this quite short and simple.

Zenering injects majority carriers into the base. They
do not contribute directly to C-B current flow for the
same reason that majority carriers there naturally do
not contribute. One 2nd order effect is that the extra
majority carriers reduce the equilibrium density of
minority carriers in the base region, reducing what is
usually thought of as the C-B leakage.

Since no sane person deliberately zeners b-e
junctions on transistors that matter, it's not like it's
important.

You've overlooked fault analysis. While you are
right that no deliberate zenering is prudently done
to a transistor later used with normal active biasing,
(and expected to stay quiet or maintain its beta),
fault conditions can lead to such "abuse". Then,
the question becomes: What comes out of (or into)
the collector? If that matters, then the answer does.

My original interest in the problem arose from an
assignment by a mentor to go work out all the
single point failure modes in a circuit where it was
thought to matter. I'm sure he planned to check
that work thoroughly, but the puzzle question was
one where he doubted the result I claimed and so
I had to persuade him, which I did. Since then, I
used it to sort out the posers from the knowers in
interviews where appropriate.

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

 

[JeffM]

The pop-tronics surf synthesizer used a back biased E-B junction
as the basic white noise source.
Don't try this trick with a Darlington
unless you want an only slightly random saw tooth.
Ken Smith

Somebody putting those suckers in the wrong drawer again?

the meter on the collector circuit twitches up scale
just as there is a bright flash and a loud bang.

Do you have a klaxon rigged to the switch of your bench supply?

 

[John Larkin]

On Sat, 19 Mar 2005 20:25:45 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

Zenering injects majority carriers into the base. They
do not contribute directly to C-B current flow for the
same reason that majority carriers there naturally do
not contribute. One 2nd order effect is that the extra
majority carriers reduce the equilibrium density of
minority carriers in the base region, reducing what is
usually thought of as the C-B leakage.

Does it really work that way? The Pease thing suggests that the zener
lights up and illuminates the c-b junction, which would cause
photodiode-mode leakage. So there would be opposing effects, I
suppose.

There are, somewhere on the web, some cool microphotographs of light
pouring out of planar transistor b-e junctions.

Since then, I
used it to sort out the posers from the knowers in
interviews where appropriate.

So, you won't hire people who don't know about this?


John

 

[Fred Bloggs]

Larry Brasfield wrote:

Zenering injects majority carriers into the base. They
do not contribute directly to C-B current flow for the
same reason that majority carriers there naturally do
not contribute. One 2nd order effect is that the extra
majority carriers reduce the equilibrium density of
minority carriers in the base region, reducing what is
usually thought of as the C-B leakage.

Purely descriptive nonsense and absent of any real meat like the energy
band theory of solids.

My original interest in the problem arose from an
assignment by a mentor to go work out all the
single point failure modes in a circuit where it was
thought to matter. I'm sure he planned to check
that work thoroughly, but the puzzle question was
one where he doubted the result I claimed and so
I had to persuade him, which I did.

There you go again with another of these incessant "let me tell you how
I put someone down again" stories...pathetic.

Since then, I
used it to sort out the posers from the knowers in
interviews where appropriate.

Really? Too bad you can't self-sort.

 

[Jim Thompson]

On Sat, 19 Mar 2005 19:19:59 -0800, John Larkin
<jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

[snip]

But zenering a transistor does permanently damage to beta, so once
it's a zener, it's always a zener.

Does anybody know how much zenering (in coulombs or whatever) it takes
to hurt a common small-sig transistor?


[snip]

John

About three days at 1mA and 100°C will cause the "zener" voltage to
collapse in "D" type plastic packages.

...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.