Zener : 9 different values from 2.7V up to 30V, all from the ZPD series bar one, the 6.8V one which is a ZTK. Go figure.
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The ZTY 6V8 diode is not a standard zener. It's a temperature compensated voltage reference. Basically a 6V2 zenner in series with a silicon diode. The positive temperature coefficent of the zener is cancelled by the negative of the diode.
If you check it wirh a DMM on diode check it will read open in both directions. This is because the two diodes are back to back. You have to check it in reverse with a current limited source of >7 V
It's a ZTK not ZTY. I googled but didn't find any ZTY Zener series.
Anyway the ZTK datasheet does say that it's temperature compensated, I did note that yesterday when I pulled the datasheet, but didn't know what to think of it...I mean datasheet headlines often use all sorts of buzz words to make you believe that your very common this or that part, is extra-ordinary and so much better than the others.... so I always take it with a pinch of salt.
However they don't say that it uses an extra diode in there for compensation, and indeed when I measure it, there is none. It measures just like any regular Zener.
So they must use some other kind of mechanism to achieve that compensation...
Anyway, I didn't know that there were temperature compensated Zener diodes, never mind that, at least some of them, did that by adding an extra diode in there.
So... thanks for the info ! ![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
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6.8v was a standard Zener voltage back in the "dreamtime", along with 5.6v .
I remember having to build a project with somewhat non standard logic levels, because 6.8v Zeners were all that were stocked in the TV site store, way out in the middle of a wheat farmers paddock.
The monster thing used 4000 series CMOS, & some TTL stuff.
It operated a switchable audio oscillator, & some 4066 switches, along with some relays, to automatically send test tones, terminations, etc to perform a programme line test from an unattended Studio.
Everybody said "Use a micro", but I knew zilch about them, so all the "smart" stuff was done with a 555, a bunch of gates, a 4017 & a "diode matrix".
It worked, but "never fired a shot in anger!"