oh. good point.
--
John Larkin, President Highland Technology Inc
Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Then what stops them?
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
to
=A0 =A0 ...Jim Thompson
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=A0 | =A0 =A0 et =A0 =A0 =A0|
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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.
[snip]
Precise small-signal slope (assuming no resistive part) is kT/qI, or ~26/I(in mA) at 300°K ...Jim Thompson
Tada!
the
an
apt.
Not at all, more like 30 seconds. Sometimes i have other things to do besides read Usenet. Tough it out pumpkin.
?-)
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Yup, the ohmic part has a positive TC.
Yawn.
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Huh? It does, but George was taking about the kT/qI portion...
450/300=1.5 ;-) ...Jim Thompson
ave to
=A0 =A0 =A0 ...Jim Thompson
=A0 =A0 =A0| =A0 =A0mens =A0 =A0 |
=A0 =A0 | =A0 =A0 et =A0 =A0 =A0|
=A0 =A0|
=A0 =A0 =A0 =A0 |
=A0|
|.- Hide quoted text -
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'.
Figure 3 in the 1n4148 data sheet that someone linked to.
(I'd just been thinking about the Wiedeman-Franz law from Jamie's MAF post.)
George H.
=A0 =A0 ...Jim Thompson
=A0 =A0| =A0 =A0mens =A0 =A0 |
=A0 | =A0 =A0 et =A0 =A0 =A0|
=A0|
=A0 =A0 =A0 |
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Yes, I thought you were. JT's comment didn't make sense.
That's British for "whining", isn't it? How is that pronounced?
--
John Larkin, President Highland Technology Inc
Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Sometimes a troll is just a troll...
to
[snip]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
I find it easier to just killfile krw. ...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 | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
m
at have to
N=A0 =A0 =A0 =A0 ...Jim Thompson
e KOh, I'm all set up to do that. (testing diode thermometers) Here's a link...(Image shack now wants me to register, so that's the end of that.)
I could only get to 10mA. (The most my current source will do.) So not into the ohmic region. The straight line is drawn by eye.
George H.
=A0 =A0 ...Jim Thompson
=A0 =A0| =A0 =A0mens =A0 =A0 |
=A0 | =A0 =A0 et =A0 =A0 =A0|
=A0|
=A0 =A0 =A0 |
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have to
[snip]Various model cards show D1N4148 with Rs (bulk resistance) = 0.56 to
0.8 Ohms ...Jim Thompson
have to
[snip]Semiconductors are notoriously difficult to measure. You have to do pulse testing to keep it from moving during the measurement. ...Jim Thompson
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