...or more accurately avalanche breakdown.
Parts tested: 2N3904 from different makers, both in normal transistor
mode (E,B,C), and in inverted mode (C,B,E); the prefix "R_" is used to
indicate this inverted or reverse mode.
All parts were bought in March 2006 and the same type and maker may
differ greatly now.
1) Central Semiconductor CMPT3904
2) Central Semiconductor CMPT3904E
3) Fairchild KST3904MTF
4) Fairchild MMBT3904
5) Diodes Inc MMBT3904-7-F
6) ON Semiconductor MMBT3904LT1G

Standard / normal mode, 20V/div horizontal, 200uA/div vertical.
For the reverse / inverted mode, 2V/div horizontal, 200uA/div
vertical; the base offset current was adjusted for a minimum observed
current (lowest trace). 0.1mA/step on the base.
Note the decided negative resistance curvature on the "zero" base
current step and none seen elsewhere (at these currents; there was
enough self-heating in the normal mode for me to dare "pushing" it).

Fred Abse wrote:
On Tue, 03 Jan 2012 21:31:07 -0800, Robert Baer wrote:

Note the decided negative resistance curvature on the "zero" base
current step and none seen elsewhere (at these currents; there was
enough self-heating in the normal mode for me to dare "pushing" it).

Doesn't your CT (I think you use a 7000 series Tek plugin, with which I'm
not familiar) incorporate pulsed measurements like a 576? It would be
nice to see where/if the asymptotes converge.

I've done unmounted SOTs up to 10 amps pulsed, with 80 microsecond
pulses, without killing them. Maybe you could brew up a pulsed test rig.

What series resistance did you use?

There's definitely avalanching going on in the "normal" mode.

Nice demonstration.

Nope, the 7CT1N does not have a pulsed mode and does not allow one to
change resistors.
*
I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).

Fred Abse wrote:
On Wed, 04 Jan 2012 19:28:40 -0800, Robert Baer wrote:

I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).

I don't see it. There's a definite negative resistance slope on the
forward traces, but I see none on the reverse characteristics.

Some traces (CMPT3904E, KST3904MTF) show signs of breaking into
oscillation at higher base currents. I've found that, usually, that's down
to parasitic L and C in the fixture, but in doesn't have to be.

yes..you are right; mis-remembered. I guess i should have pushed them
more in the inverted mode, but did not want to do any permanent damage.

On Thu, 05 Jan 2012 20:06:36 -0800, Robert Baer
wrote:

Fred Abse wrote:
On Wed, 04 Jan 2012 19:28:40 -0800, Robert Baer wrote:

I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).

I don't see it. There's a definite negative resistance slope on the
forward traces, but I see none on the reverse characteristics.

Some traces (CMPT3904E, KST3904MTF) show signs of breaking into
oscillation at higher base currents. I've found that, usually, that's down
to parasitic L and C in the fixture, but in doesn't have to be.

yes..you are right; mis-remembered. I guess i should have pushed them
more in the inverted mode, but did not want to do any permanent damage.

I've cracked the BVceo shape with a simple TANH function... watch for
ensuing developments... I'm convinced I can model it.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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

On Thu, 05 Jan 2012 22:20:29 -0700, Jim Thompson
wrote:

On Thu, 05 Jan 2012 20:06:36 -0800, Robert Baer
wrote:

Fred Abse wrote:
On Wed, 04 Jan 2012 19:28:40 -0800, Robert Baer wrote:

I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).

I don't see it. There's a definite negative resistance slope on the
forward traces, but I see none on the reverse characteristics.

Some traces (CMPT3904E, KST3904MTF) show signs of breaking into
oscillation at higher base currents. I've found that, usually, that's down
to parasitic L and C in the fixture, but in doesn't have to be.

yes..you are right; mis-remembered. I guess i should have pushed them
more in the inverted mode, but did not want to do any permanent damage.

I've cracked the BVceo shape with a simple TANH function... watch for
ensuing developments... I'm convinced I can model it.

...Jim Thompson

Like the attachment.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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

Jim Thompson wrote:
On Thu, 05 Jan 2012 22:20:29 -0700, Jim Thompson
wrote:

On Thu, 05 Jan 2012 20:06:36 -0800, Robert Baer
wrote:

Fred Abse wrote:
On Wed, 04 Jan 2012 19:28:40 -0800, Robert Baer wrote:

I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).
I don't see it. There's a definite negative resistance slope on the
forward traces, but I see none on the reverse characteristics.

Some traces (CMPT3904E, KST3904MTF) show signs of breaking into
oscillation at higher base currents. I've found that, usually, that's down
to parasitic L and C in the fixture, but in doesn't have to be.

yes..you are right; mis-remembered. I guess i should have pushed them
more in the inverted mode, but did not want to do any permanent damage.
I've cracked the BVceo shape with a simple TANH function... watch for
ensuing developments... I'm convinced I can model it.

...Jim Thompson

Like the attachment.

...Jim Thompson
VERY nice!!

On Fri, 06 Jan 2012 12:03:28 -0800, Robert Baer
wrote:

Jim Thompson wrote:
On Thu, 05 Jan 2012 22:20:29 -0700, Jim Thompson
wrote:

On Thu, 05 Jan 2012 20:06:36 -0800, Robert Baer
wrote:

Fred Abse wrote:
On Wed, 04 Jan 2012 19:28:40 -0800, Robert Baer wrote:

I think that the curves also show definite avalanche mode for the
inverted mode...at least for the right base condition(s).
I don't see it. There's a definite negative resistance slope on the
forward traces, but I see none on the reverse characteristics.

Some traces (CMPT3904E, KST3904MTF) show signs of breaking into
oscillation at higher base currents. I've found that, usually, that's down
to parasitic L and C in the fixture, but in doesn't have to be.

yes..you are right; mis-remembered. I guess i should have pushed them
more in the inverted mode, but did not want to do any permanent damage.
I've cracked the BVceo shape with a simple TANH function... watch for
ensuing developments... I'm convinced I can model it.

...Jim Thompson

Like the attachment.

...Jim Thompson
VERY nice!!

Thanks! It's nothing more than a TANH behavioral source and two
resistors, which I figure to ultimately connect between collector and
base. Right now, "fit" is hit or miss, so I'm trying to break it up
into something where parameterization is straight forward... some
messy math in store for me. Stay tuned ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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