Re: Logarithmic response of PN junctions


"Rich Grise, Plainclothes Hippie" <eatmyshorts@xxxxxxxxxxxxxxx> wrote in
message news:pan.2006.08.03.22.30.14.815251@xxxxxxxxxxxxxxxxxx
I was just musing about "log amps", where they exploit the
exponential/logarithmic relationship between the current and
voltage of a PN junction.

My question is, is that always "log e", ie., "ln"? My point
being, is it _always_ base "e", rather than, say, log 10, or
log 2, or log something else?

Is that true for silicon, germanium, gallium arsenide, every
semiconductor?

Is that why they're called "natural logs"? If that's true, I
actually find it kind of spooky! :-)

Thanks!
Rich

It doesn't make any difference. Log, Ln they are both the same curve and
vary only in constants. Remember you can change the base of a logarithm by
simply dividing by the log of the other base, a constant. For example: logA
= lnA/ln10. And, lnB = logB/loge. You can change to any arbitrary base, 2,
hex, octal, whatever, the curve and the math is the same. The word "natural"
has to do with the base e, 2.718....and its relationship to trig functions,
vectors and other relations of higher mathematics, not to PN junctions.
Bob


.

Relevant Pages

  • Re: Is a neutral metal-semiconductor junction possible?
    ... This makes sense for two identical materials, but if for example, an n-type semiconductor with a wide forbidden band gap and a metal somehow had the same work functions and were joined, I appreciate that there would be no built-in potential barrier, but wouldn't a Schottky barrier be formed due to the position of the conduction band edge over the common Fermi level? ... In principle, these junctions should behave like normal Schottky diodes, turning on with a voltage that pushes the semiconductor majority carriers toward the junction. ...
    (sci.engr.semiconductors)
  • Re: Lifford East/West Junctions
    ... but does not use the curve between the Lifford East ... York train was routed via Solihull, Bordesley Junction, St Andrew's ...
    (uk.railway)
  • Re: Kings Cross Incline - Youtube video help.
    ... Liverpool St. line at the junction just outside Hackney Central? ... The curve between Dalston Kingsland and London Fields is the Graham Road ... put in when Broad Street was closed, to enable the peak Broad Street to ...
    (uk.railway)
  • Re: Is a neutral metal-semiconductor junction possible?
    ... only a true neutral junction can be ... >> semiconductor with a wide forbidden band gap and a metal somehow had ... >> formed due to the position of the conduction band edge over the common ... The neutral junction condition thus requires degenerate n-type doping, ...
    (sci.engr.semiconductors)
  • Re: Lifford East/West Junctions
    ... Hill is frequently used, but does not use the curve between the Lifford East ... The curve was used a few years back during the Proof House Junction ... York train was routed via Solihull, Bordesley Junction, St Andrew's ...
    (uk.railway)