At 10:40 AM 3/13/2004 +1300, you wrote:

>Regrettably a quick Google did not produce any references. Someone here
>should be able to comment.

Pease told me it's based on a technique first published by Tektronix in
a (human) generation ago ('68?). The major inaccuracy is from the base
spreading resistance parameter. I've only used it over "normal"
temperature range (-40 - 125=B0C).

One issue (other than complexity) with doing it that way is that the
sensitivity for a 10:1 difference in current is reduced about an order
of magnitude- to around 200 microvolts per Kelvin. NOTE: I'm not sure
how well  it works at very low temperatures- below 100 Kelvin the
diode voltage does strange things.

Thermocouples, OTOH, are interchangable as made (no calibration), but
have even lower output (perhaps 7 microvolts per Kelvin) and require
cold-junction compensation circuitry.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the=
 reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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