J
John Fields
Guest
On Thu, 09 Feb 2012 10:31:48 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
You've done well, Jim, congratulations.
--
JF
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
---On Thu, 09 Feb 2012 10:55:03 -0600, John Fields
jfields@austininstruments.com> wrote:
On Wed, 08 Feb 2012 11:49:37 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:
On Wed, 08 Feb 2012 08:49:11 -0800, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 8 Feb 2012 07:32:11 -0800 (PST), George Herold
gherold@teachspin.com> wrote:
On Feb 8, 9:48 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Tue, 07 Feb 2012 22:09:33 -0800, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Tue, 7 Feb 2012 19:39:47 -0800 (PST), George Herold
gher...@teachspin.com> wrote:
On Feb 7, 9:53 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Tue, 07 Feb 2012 18:40:31 -0800, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sun, 5 Feb 2012 17:22:24 -0800 (PST), dagmargoodb...@yahoo.com
wrote:
On Feb 5, 5:39 pm, Jim Thompson wrote:
On Sun, 05 Feb 2012 14:08:18 -0800, John Larkin wrote:
On Sun, 05 Feb 2012 13:28:58 -0700, Jim Thompson wrote:
So far, life has been a huge amount of fun. But what does that have to
do with diodes?
The same as talking amps of current in a 1N4148.
http://www.nxp.com/documents/data_sheet/1N4148_1N4448.pdf
Looks effectively ohmic above 50mA (Fig. 3).
Yup. The slope is just about 1 ohm. The dynamic impedance of a PN
junction is 1 ohm at 25 mA.
Closer to 26mA ;-)
...Jim Thompson
--
[snip]
- Show quoted text -
1 ohm is a pretty good number for a small junction. I measured a
2n3904 about the same.
Neat, how the resistance goes to ~1.5 ohms at ~450K.
George H.
Yup, the ohmic part has a positive TC.
Huh? It does, but George was taking about the kT/qI portion...
450/300=1.5 ;-)
Opps, I was talking about the resistive part. It should also scale
with the absolute temperature, if the resistance is from some hunk of
'metal'.
Yes, I thought you were. JT's comment didn't make sense.
Why? Because you don't understand kT/qI ?
Perfect diode, no resistive term, DYNAMIC impedance scales linearly
with temperature (°K). So a perfect diode operating a 26mA at 300°K
has a DYNAMIC impedance of 1 Ohm; and 1.5 Ohm DYNAMIC impedance at
450°K.
Perhaps someone would plot 1N4148 forward drop on LOG paper so we can
easily see the bulk R breakpoint (and the _dirt_ at low currents, the
ISR coefficient in the model).
...Jim Thompson
---
Not 1N4148 per se, but silicon in general.
news:r1u7j79mdi2c4g5bdtpcap7f1oopccrkup@4ax.com
From Motorola's 1980 silicon rectifier data manual.
Yep. Actually, that double curve reminds me that, if you do that for
IB _and_ IC of a _transistor_, you can derive all kinds of model
parameters. I did that, with assistance from my son Aaron, in the
early '80's writing the solution of that problem as a Pascal
executable. (Damn! I thought nothing of it then, but Aaron was only
12 years old at the time! He's gone on to be in charge of all
software creation and utilization for the world's largest call-center
corporation... working from his farm house in San Tan Valley, AZ
...Jim Thompson
You've done well, Jim, congratulations.
--
JF