a break from disease

J

John Larkin

Guest
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On 20.3.20 20:25, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.
Click to expand...

Did you try the transdiode connection - C to B shorted?

It is what the analog guys like for precision diode.

--

-TV
 
On 3/20/2020 2:25 PM, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.
Click to expand...

Looks almost use-able as a voltage-controlled resistor with a reverse
beta of ~4 over 5mA
 
On 20/03/2020 18:25, John Larkin wrote:
https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1
Click to expand...

I don't understand the last two sets of data (with base supply negative)
- is that because Ib is now part of Ic flowing into the base voltage
supply - can one say it has beta then?

piglet
 
On Fri, 20 Mar 2020 16:48:02 -0500, John S <Sophi.2@invalid.org>
wrote:

On 3/20/2020 1:25 PM, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.


It is sometimes difficult to decode your uA from you mA. Try printing
better or use a sharper point on your pen.
Click to expand...

Where are the units not obvious?

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On 3/20/2020 1:25 PM, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.
Click to expand...

It is sometimes difficult to decode your uA from you mA. Try printing
better or use a sharper point on your pen.
 
On Friday, March 20, 2020 at 2:25:59 PM UTC-4, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.
Click to expand...

That was me... I guess I should try and measure the gain at
~1 MHz and 10nA to 1 uA.. or something like that.

So silly question; Are your graphs at what I would call reverse bias?
Collector negative wrt emitter.(and base)
Well the second one Vb-e you've left the collector floating?

George H.
--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Click to expand...
 
On Sat, 21 Mar 2020 10:37:50 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

On Friday, March 20, 2020 at 2:25:59 PM UTC-4, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.

That was me... I guess I should try and measure the gain at
~1 MHz and 10nA to 1 uA.. or something like that.
Click to expand...

Really low-current beta would be interesting.

So silly question; Are your graphs at what I would call reverse bias?
Collector negative wrt emitter.(and base)
Click to expand...

The reverse-beta one was. The fA leakage graph goes both ways.

>Well the second one Vb-e you've left the collector floating?

Yes. That's just to characterize the b-e junction and emitter
resistance. I was wondering at what current the b-e diode would go
ohmic, but it's past my last 10 mA point. I've been doing some Spice
sims that may not agree with real life. Maybe my model needs tweaking.
Needs more work.

George H.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Click to expand...

--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On Sat, 21 Mar 2020 11:51:42 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Saturday, March 21, 2020 at 11:05:23 AM UTC-7, jla...@highlandsniptechnology.com wrote:
On Sat, 21 Mar 2020 10:37:50 -0700 (PDT), George Herold
ggherold@gmail.com> wrote:


Well the second one Vb-e you've left the collector floating?

Yes. That's just to characterize the b-e junction and emitter
resistance.

But, that doesn't tell you the emitter resistance; it tells you Rbb,
the base spreading resistance. There's not much Rbb contribution
when the collector is taking most of the current, it's collector-connected-to-base
that tells you the emitter resistance.
Click to expand...

The base-emitter curve is exponential to 10 mA, which means that the
emitter resistance is low enough that I don't have to worry about it
in my current application. I guess I could try to resolve the two
resistances somehow.

It's an amazing diode. Maybe half a pF, a few fA leakage, pretty low
series resistance. C-B is similar but good for more voltage. It's
miles better than a PAD-1.

Small schottkies are mostly ohmic at 10s of mA. There's a zero forward
TC point there, too.


--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On Sat, 21 Mar 2020 15:05:04 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-03-20 14:25, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.


*sniff sniff* a thing of beauty, for sure. Almost as good as the BFG25A.

Cheers

Phil Hobbs
Click to expand...

That was the same chip in SOT-143 wasn't it? Long gone.



--

John Larkin Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
 
On 2020-03-20 14:25, John Larkin wrote:
We were talking about BFT25 somewhere.

https://www.dropbox.com/s/ft0tsikhdi90rgq/BFT25.JPG?raw=1

https://www.dropbox.com/s/28cxa6b8pl54ltk/BFT25_B-E.jpg?raw=1

https://www.dropbox.com/s/h6ykxgeyym7djjb/BFT25_rev_Beta.JPG?raw=1

The junctions look logarithmic from about 100 fA to 10 mA, as far as I
went. Must be a really tiny thing.
Click to expand...

*sniff sniff* a thing of beauty, for sure. Almost as good as the BFG25A.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Saturday, March 21, 2020 at 11:05:23 AM UTC-7, jla...@highlandsniptechnology.com wrote:
On Sat, 21 Mar 2020 10:37:50 -0700 (PDT), George Herold
ggherold@gmail.com> wrote:


Well the second one Vb-e you've left the collector floating?

Yes. That's just to characterize the b-e junction and emitter
resistance.
Click to expand...

But, that doesn't tell you the emitter resistance; it tells you Rbb,
the base spreading resistance. There's not much Rbb contribution
when the collector is taking most of the current, it's collector-connected-to-base
that tells you the emitter resistance.
 
>That was the same chip in SOT-143 wasn't it? Long gone.

The BFG and BFU series are/were faster but otherwise similar. The BFG25A/X was an improved drop-in replacement for the venerable and beloved MRF9331.

The regular BFG25A came in the normal SOT23, iirc.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
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