Zener diodes are built as true Zener only up to a certain (low) voltage
and exhibit a negative temperature coefficient. From a certain voltage
and up, they are indeed avalanche diodes and have a positive temperature
coefficient.


Isaac



Em 30/01/2012 21:12, Steve Smith escreveu:
> Use a TL431 and two resistors far more stable than a zener.=20
>
> More current it will heat and they are slightly positive temp coefficient=
..
> We used to use 3v9's years ago and they were slightly -ve temp coefficien=
t
> BZ88's if I am remember...
>
> Gave up with zeners and only use them for power supply's and shit stopper=
s
> now 431's are far better...
>
> Steve
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf =
Of
> alan smith
> Sent: 30 January 2012 23:09
> To: Microcontroller discussion list - Public.
> Subject: [EE] zener voltage slowly rising
>
> what might cause a zener voltage to slowly rise?  Load isnt changing, its
> constant, driving into an opamp to distribute the voltage.  Its a 8.2V pa=
rt,
> MMSZ5273B with a 10K series.  It starts at 8.28V, over 5 min rises to
> 8.321V.  Cooling it down..drops it so its temp related....current related=
?=20
> Too much current so it heats up?  Source is 19V as well.
>
>

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.