Re: Vbe stuff

Jonathan Kirwan wrote:

On Sun, 15 Oct 2006 12:09:17 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:


On Sun, 15 Oct 2006 17:50:26 GMT, Jonathan Kirwan
<jkirwan@xxxxxxxxxxxxxx> wrote:


On Sun, 15 Oct 2006 09:51:18 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:


On Sun, 15 Oct 2006 16:24:30 GMT, Fred Bloggs <nospam@xxxxxxxxxx>
wrote:


Jim Thompson wrote:


Density has nothing to do with vbe change per decade _provided_ you're
not into where resistance is affecting the measurement.

...Jim Thompson

I suppose it has more to do with a design goal minimizing conduction losses in the high current diode thereby prohibiting the use of very large ratios of majority doping material density as with the transistor. This will cause a departure from the simplified minority carrier density at the transition region boundaries as a function of forward bias because the minority carrier density on both sides of the transition region change significantly with a coupled dependence.

As someone else pointed out, the 1N4xxx devices are also very lightly
doped (almost PIN-diode-like) to get the "high-voltage" performance.

But, Fred, your dissertation sounds just like that... dissertation out
of the mouth of some _twisted_ PhD ;-)

All the same, it makes some sense to me. Shockley's equation develops

from an assumption that the forward current is entirely due to

minority carrier diffusion in neutral regions, I think. I need to
think more about it, but on first cut it sounds like the right
direction.

Jon

Large ratios of doping level are precluded by (primarily) breakdown
voltage and forward resistance considerations.


But isn't forward resistance a valid part of this measurement being
discussed?

Jon
At 100uA, the IR drop is not significant.
.

Relevant Pages

  • Re: Vbe stuff
    ... Jim Thompson wrote: ... This will cause a departure from the simplified minority carrier density at the transition region boundaries as a function of forward bias because the minority carrier density on both sides of the transition region change significantly with a coupled dependence. ... The measurement deviations are not about non-linearity due to Is dependence on injection level or anything like that. ...
    (sci.electronics.design)
  • Re: Vbe stuff
    ... Jim Thompson wrote: ... not into where resistance is affecting the measurement. ... This will cause a departure from the simplified minority carrier density at the transition region boundaries as a function of forward bias because the minority carrier density on both sides of the transition region change significantly with a coupled dependence. ...
    (sci.electronics.design)
  • Re: Vbe stuff
    ... not into where resistance is affecting the measurement. ... This will cause a departure from the simplified minority carrier density ... because the minority carrier density on both sides of the transition ... But isn't forward resistance a valid part of this measurement being ...
    (sci.electronics.design)
  • Re: Multimeters (My first post to sci.electronics.basics)
    ... I set up two small lamps in series, and test the resistance ... > measured with the same multimeter as used to measure the total ... measurement current from the meter. ... If that's the case, each bulb has ...
    (sci.electronics.basics)
  • Chapter 19A from "Reflections III" - Step 2 response
    ... circuit (from plate to ground) with an HP-4815 Vector Impedance Meter. ... The resistance is found to be approximately 1400 ohms. ... one measurement made from the plate ...
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