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#Post#: 24--------------------------------------------------
Set Diode Properties
DIR By: kenarton
Date: September 8, 2023, 4:56 pm
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Hi,
I have placed a zener diode in my circuit, using MODEL=$GENERIC.
The circuit is simply: +10v -- 10k resistor -- Zener -- GND
I want to set its voltage to 4.7v, so I click on it to bring up
the properties panel.
My first thought was that the second parameter in the list which
is VALUE, should be its breakdown voltage,
so I set it to 4.7. But when I hover the mouse on it the
description at the bottom says it is the Diode Area Multiplier.
When I run DC analysis it shows 10v across it, and zero current
flow.
Other circuitry in the same schematic is working exactly as
expected.
How do I set the breakdown voltage ? It seems I am missing
something obvious!
I have searched the very comprehensive user guide for "zener",
but found nothing.
Searching for "diode" is equally useless.
Any suggestions ? Thanks, Ken.
#Post#: 26--------------------------------------------------
Re: Set Diode Properties
DIR By: MC12
Date: September 8, 2023, 6:46 pm
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I'm not in a position to check at the moment, but in a day or
two I'll see whether I can replicate this and we'll go from
there.
#Post#: 31--------------------------------------------------
Re: Set Diode Properties
DIR By: kenarton
Date: September 9, 2023, 4:39 am
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Thanks, I'll look out for that.
#Post#: 32--------------------------------------------------
Re: Set Diode Properties
DIR By: MC12
Date: September 13, 2023, 6:18 am
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Okay... so I had to refresh my memory a bit!
If instead of going for Analog Primitives > Passive Components >
Zener you select a device from Analog Library > Diode > Zener
(eg 1N750 is 4.7V), then right-click Edit Item..., in the table
of modelling values is "BV 4.7" – which as a pretty good guess
represents Breakdown Voltage.
The BV field for the generic part is preset at 500. Either
change that to 4.7, or use a 4.7V zener model from the diode
library in the first place.
#Post#: 33--------------------------------------------------
Re: Set Diode Properties
DIR By: kenarton
Date: September 16, 2023, 5:31 am
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Hello,
Apologies for delay in replying -- the notifying email went to
my junk folder.
Anyway, I have followed your instruction, and it is fine now, I
can set Zener BV.
I now know to use Analog Library rather than Analog Primitives.
Many thanks for your help. Ken.
#Post#: 34--------------------------------------------------
Re: Set Diode Properties
DIR By: MC12
Date: September 16, 2023, 10:17 am
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--- Quote from: kenarton link ---
>
> the notifying email went to my junk folder.
--- End Quote ---
Sounds familiar! ;D
--- Quote ---
>
> Anyway, I have followed your instruction, and it is fine now,
I can set Zener BV.
> I now know to use Analog Library rather than Analog
Primitives.
> Many thanks for your help. Ken.
>
--- End Quote ---
I'm pleased I could help, thanks. I don't think it is essential
to avoid the primitives, it's just a case of knowing which
parameter does what. It wasn't until I specifically used a 4.7V
zener model and could look for a parameter with "4.7" as the
value that I knew the relevant parameter is "BV", and I think if
one were to type that into the "Value" box it would have to be
"BV=4.7" rather than just "4.7".
#Post#: 35--------------------------------------------------
Re: Set Diode Properties
DIR By: kenarton
Date: September 16, 2023, 11:07 am
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Hi, Using the generic Zener diode from Analog Primitives, as
you say, the tables in three columns shows BV set to 500. I
cannot find any way to change this in the table. I have tried
inserting "BV=4.7" for the Value parameter (without the quote
marks), but the DC analysis will not run; it puts red octagon on
the diode and says:
Warning: Extra text 'BV=5.0' found. Anyway, I am not really
bothered as long as I can get a settable zener from the Analog
Library. Thanks again, Ken.
#Post#: 36--------------------------------------------------
Re: Set Diode Properties
DIR By: MC12
Date: September 17, 2023, 7:45 am
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It ought to be possible to change the generic model values
though, I'll investigate...
#Post#: 37--------------------------------------------------
Re: Set Diode Properties
DIR By: MC12
Date: September 18, 2023, 2:45 am
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I didn't have any difficulty editing the BV value in the
relevant box (right-click then Edit Item). Simulation shows
this working.
HTML http://i.imgur.com/NVCqLEsm.jpg
HTML https://imgur.com/NVCqLEs
#Post#: 39--------------------------------------------------
Re: Set Diode Properties
DIR By: Rohit
Date: October 6, 2023, 10:50 am
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Also if you set BV=4.7, actual break down voltage will be
somewhat higher (this is not a MC specific behavior, this is how
diodes in spice work) to get get breakdown voltage same as BV,
tweak other parameters. e.g. setting the value of N (Emission
coefficient) to a small value (~1m) gets you the desired result.
[attachimg=1]
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