Re: Question about diode temperature and forward voltage
- From: Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx>
- Date: Tue, 13 Jun 2006 22:18:08 -0700
acataldo@xxxxxxxxx wrote:
I'm trying to understand how a diode can be used to detect changes inwhat your missing is the way it's being used
temperature. According to all the literature I've read, a diode's
forward voltage, Vf, falls by 2 mV for every 1 degree C increase in
temperature. This doesn't seem to agree with the diode equation, which
suggests that Vf should increase with temperature.
Vf = k*T/q * ln( If / Is)
What am I missing?
in the circuit.
diodes start conducting better as they get
warmer.
if you were to have a diode in a series
circuit and measure voltage that way, then you
would get the increase as indicated how ever
what i think your looking at is the diode being
used as a shunt load..
as the diode warms up it conducts better and there
for dropping the voltage on the load.
normally 2 diodes in series are used into a pot that
drive's the base of a transistor.
the pot, is to calibrate the bias point.
--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
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