[sdiy] [OT] PTAT with PN junction

[patchell]

    Like Martin said earlier...the forward drop has a tempco of about
-2mV/K (or per C as well)))...but like it states below, and as I have
learned myself in the last few months, one junction by itself is not a
great way to measure temperature...

    For more information, the Art of Electronics has a great explanation of
Band Gap References in it...it even gave me some potontial ways of
simplifiying a way to do this (as opposed to the way I did it recently in
the VCO I did), and someday, I will have to give it a try...

ASSI wrote:

> On Thursday 13 March 2003 07:44, Tim Ressel wrote:
> > There seems to be a hole in my knowledge. I an using a
> > transistor PN junction as a temperature sensor (PTAT)
> [...]
>
> What you really want is two junctions at the same temperature forward
> biased with different current densities, a single junction is never
> proportional to anything. In integrated circuits this is simply done by
> scaling the area of one versus the other so you can use a current
> mirror to drive both at the same current. With discretes, it is usually
> simpler to just use two different currents (the current ratio needs to
> be controlled carefully), otherwise you need an array and gang 7 vs. 1
> diode or some such.
>
> Check out the design manual at http://www.arraydesign.com for instance
> for the gory details and lots of useful ideas on bipolar circuits
> (especially the section on deltaVbe).
>
> Achim.
> -- +<[ Q+ & Matrix-12 & WAVE#46 & microQkb Omega sonic heaven ]>+ --
>
> Q/Q+ MIDI Implementation & additional documentation:
> http://homepages.compuserve.de/Stromeko#WaldorfQDocs

--
 -Jim
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