Zeners in series
Steve Kraus
the same polarity the effect is the same as having one zener of the sum of
the two voltages, right?
Michael A. Terrell
Yes, as long as you don't exceed the curent either diode is rated
for. If you do, that diode will overheat and short.
--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
N_Cook
news:TsGdnTFrO6H_ylfR...@earthlink.com...
> Just wanted to be sure of this. If you connect two zeners in series with
> the same polarity the effect is the same as having one zener of the sum of
> the two voltages, right?
While at it 2 diacs in series , assuming 2x 8V ones , would give 8V ?
What if high ohm balancing R across each, too high to turn on the associated
device?
Arfa Daily
"Steve Kraus" <scr...@SPAMBLOCKfilmteknik.com> wrote in message
news:TsGdnTFrO6H_ylfR...@earthlink.com...
> Just wanted to be sure of this. If you connect two zeners in series with
> the same polarity the effect is the same as having one zener of the sum of
> the two voltages, right?
Basically, yes. I do it all the time. Doesn't usually work out *quite*
right, but close enough as not to normally matter.
Arfa
N_Cook
news:Dnvyo.19007$7p5....@newsfe22.ams2...
And to adjust for the odd 1/4 or 1/2 a volt more, add a normal diode or 2 in
the chain
Arfa Daily
"N_Cook" <div...@tcp.co.uk> wrote in message
news:iae09e$gh0$1...@news.eternal-september.org...
Quite
Arfa
David Nebenzahl
> Just wanted to be sure of this. If you connect two zeners in series with
> the same polarity the effect is the same as having one zener of the sum of
> the two voltages, right?
Done all the time (2 or more diodes in series). You can even take
intermediate voltages from taps in a series string of zeners.
--
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with the flaunting of well-defined muscle, wrapped in flags.
- Comment from an article on Antiwar.com (http://antiwar.com)
Art Todesco
> On 10/28/2010 10:10 PM Steve Kraus spake thus:
>
>> Just wanted to be sure of this. If you connect two zeners in
>> series with the same polarity the effect is the same as having one
>> zener of the sum of the two voltages, right?
>
> Done all the time (2 or more diodes in series). You can even take
> intermediate voltages from taps in a series string of zeners.
>
care", however, in some applications, it might enter into the
equation, so you have to double that.
David Nebenzahl
It's still the usual 0.7 V per junction, right?
who where
<nob...@but.us.chickens> wrote:
>On 10/28/2010 10:10 PM Steve Kraus spake thus:
>
>> Just wanted to be sure of this. If you connect two zeners in series with
>> the same polarity the effect is the same as having one zener of the sum of
>> the two voltages, right?
>
>Done all the time (2 or more diodes in series). You can even take
>intermediate voltages from taps in a series string of zeners.
and you can tweak the overall tempco by selection of the elements to
combine.
Damon Hill
news:6ulmc61qmkng6t480...@4ax.com:
Don't forward-biased silicon diodes have a tempco reverse that of
a zener diode? If I want a temperature-compensated 40VDC, I could
combine a 39 volt zener and a diode or two and get very close to
40 volts with minimum drift.
--Damon
isw
Damon Hill <damon...@comcast.netnet> wrote:
There's a natural "turnover point" at something about 5.6 volts for
reverse-biased diode junctions. For breakovers below that voltage, the
Zener effect predominates, and the devices exhibit a negative tempco.
Above it, the avalanche effect becomes predominant, with a positive
tempco. Right around 5.6 volts, the tempco can be very near to zero. You
can make composite devices with very low tempco for voltages well above
5.6 devices by putting one (or more) of each type in series.
So if you wanted, say, a 40volt stable reference, you'd probably get
best performance by putting (say) a 36 volt device and a 4 volt device
in series -- or maybe 37 volts and 3 volts; check the tempco curves. And
be sure to thermally connect the two devices together.
Isaac
Damon Hill
news:isw-F4887F.00161102112010@[216.168.3.50]:
Aha! I'd wondered why that trick wasn't used more often in an
integrated package. Thanks for the explanation.
--Damon
isw
Damon Hill <damon...@comcast.netnet> wrote:
While we're talking about stable references, the way to get a
low-voltage one (2 volts, say), is to thermally tie together 20 volt and
22 volt devices and take the difference between them as the reference.
The two devices (Which should be from the same manufacturer, etc.) will
drift together, leaving a constant difference.
Or, you could just use an LM-10...
Isaac
Clyde
I did this in a VCR switch mode power supply which had failed. I was
repairing on the cheap using parts I had laying around. Couldn't find a
zener of the right voltage so I put 2 in series to get as close as
possible. Worked fine.