The datasheets for the 2N7002 and BSS84 don't have a figure
for Idsoff. Could this figure be included in their models?
Does LTSpice use this figure? If so what is it called and
what would I look for in the model to determine these values?

Thanks,

Dave.

--- In LTspice@..., "Dale" <dchishol@c...> wrote:

In what companies is LTSpice used as part of the circuit design

process?

I'm expecting to receive an M.S. in Electrical Engineering in May,

and

currently have no job prospects. I'd like to join an organization
where I could explore the application of simulation in the circuit
design process. I haven't encountered any jobs where circuit
simulation is used. I'd appreciate hearing about companies where it
IS used, so I may investigate them as possible employers.

Thanks,
Dale

Dale,

You are going to use simulation in any job that requires you to do
circuit design. I think it's understood that simulation is just
another tool used in the circuit design process. To me, it's no
different than the understanding that you will use tools like a
calculator, scope, logic analyzer, or DMM. Focus on finding a job
where circuit design will be your primary responsibility. It sounds
like the job opportunities you've encountered may not actually be
true design positions. Unfortunately, it's a tough market to be
picky. Good luck in your search!

- John

I use it -at- work, but not for work related purposes. :-)




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Keep this in mind if you answer this message.

In what companies is LTSpice used as part of the circuit design process?

I'm expecting to receive an M.S. in Electrical Engineering in May, and
currently have no job prospects. I'd like to join an organization
where I could explore the application of simulation in the circuit
design process. I haven't encountered any jobs where circuit
simulation is used. I'd appreciate hearing about companies where it
IS used, so I may investigate them as possible employers.

I know that a number of people here use it unofficially. Our so-called
"prefered" simulator is SABER for some strange reason, although our ECAD does
(thank God) support Accusim -a Spice based simulator.

Both official simulators are part of an integrated tool-set that allows (in
theory anyway) design from a high level behavoural model through detail
discrete circuit and IC design and layout to PC board layout with a common
component library (physical and virtual).

You will find this to be the case in most large companies i.e. the simulator is
only one part of the picture; other tools that can take data directly from the
schematic capture are very desirable in order to avoid mistakes. There is also
the problem of configuration control of data and shared libraries(which version
are we working on ?) A large team can be working on the one design concurrently
in our ECAD environment -all seeing the current version.

The fact that LTSpice is standalone, does make it non-ideal in these respects .
However I am tending to use it more and more for small circuits or parts of
circuits or for debugging designs. The official simulators are not efficient
for this, they are better for really big hierarchical designs and data
management.

The huge "plus" is that I can run the accusim netlists on LTSPICE for sanity
checking and vice versa i.e I can attach an LTSPICE netlist to an Accusim
symbol and run it.

I am very impressed by LTSPICE and have been recommmending its use in the
context I describe. The only thing lacking is a monte-carlo (Mike ?)

Good luck in your job hunting. We have places in North America, if you don't
want to come to Scotland.



Brian


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BAE SYSTEMS | Fax: 0131 343 5050
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In what companies is LTSpice used as part of the circuit design process?

I'm expecting to receive an M.S. in Electrical Engineering in May, and
currently have no job prospects. I'd like to join an organization
where I could explore the application of simulation in the circuit
design process. I haven't encountered any jobs where circuit
simulation is used. I'd appreciate hearing about companies where it
IS used, so I may investigate them as possible employers.

Thanks,
Dale

Hello Dave,
what's about leakage currents?

Is the voltage Vgs of the BSS84 zero volt? If not, the reason is

the

Idsoff leakage current of the 2n7002.

How big is the leakage current Idsoff simulated by the model of the
BSS84 for Vgs=0?

That's what I thought initially, but the BSS84 leakage current
is only 10na max, 1na typ.

Oh wait, that's GateSource leakage, aha... They don't have a number
for either the BSS84 or the 2N7002 for Drain Source leakage. Could
this be high enough to cause 60mv of offset???

Dave.

--- In LTspice@..., "David Pariseau"
<david.pariseau@s...> wrote:

When I simulate the following circuit I end
up with 60mv for VOUT when the circuit should be off?
Any ideas why? Not sure where the voltage is coming
from.
6v
47pf Batt BSS84 VOUT
+----+---+------+----+ +-----------+--+
| + + + --- |
| --- --- .-. V .-.
| --- - | | | | |20K
| | | 1M| | | 50K | |
|-+ | === '-' | ___ '-'
+->| | GND +-----+-|___|++ |
| |-+ | | +-| + 47pf
| |----+----------+ 2N7002 |<-+---+
| 2N7002 | +-| | |
| | o | .-. |
|=|> === | | ---
VOff | o GND | | ---
Mom.Switch | '-' |
=== 500K | |
GND === ===
GND GND

Dave Pariseau.

Hello Dave,
what's about leakage currents?

Is the voltage Vgs of the BSS84 zero volt? If not, the reason is the
Idsoff leakage current of the 2n7002.

How big is the leakage current Idsoff simulated by the model of the
BSS84 for Vgs=0?


Best Regards
Helmut

When I simulate the following circuit I end
up with 60mv for VOUT when the circuit should be off?
Any ideas why? Not sure where the voltage is coming
from.
6v
47pf Batt BSS84 VOUT
+----+---+------+----+ +-----------+--+
| + + + --- |
| --- --- .-. V .-.
| --- - | | | | |20K
| | | 1M| | | 50K | |
|-+ | === '-' | ___ '-'
+->| | GND +-----+-|___|++ |
| |-+ | | +-| + 47pf
| |----+----------+ 2N7002 |<-+---+
| 2N7002 | +-| | |
| | o | .-. |
|=|> === | | ---
VOff | o GND | | ---
Mom.Switch | '-' |
=== 500K | |
GND === ===
GND GND

Dave Pariseau.

Hello Helmut,

you were faster with your second posting as I could answer your first one. I wanted to recommend the teccor company too.

I really like Teccor SCRs and TRIACs. We use them extensivelly on our company. Very expensive, but they are the best I know.

The field SpiceModel must be empty. That's the only mistake. You only add the TRIAC symbol from the "misc" directory. Then "right click" the mouse over the word TRIAC and change it to Q8025R5.
Shure, the command line with the models must be added to the schematic. Example: .INCLUDE tectriac.lib . Put this file into the lib&#92;sub directory of SwitcherCADIII.

Yes, this was my mistake. Now it's working. I still don't understand very well how to manage the LTSpice libraries, but I'm working on it.

Have you read the datasheet of this high power TRIAC? It needs nearly 100mA gate current to switch on. Just a hint for the circuit in your simulation.

This was just an example. I've imported the tectriac.lib and some triacs from OnSemi.

Thank you *very* much,

Brusque

--
-----------------------------------------------------------------
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-----------------------------------------------------------------

--- In LTspice@..., Panama Mike <panamatex@y...> wrote:

Helmut,

Hello Mike or whoever exactly knows about,
...if a model uses the node number 0, is
it then referenced to the common ground
0 of the top schematic or is this a
floating node like any other node inside
the subcircuit?

Yes you are correct, node 0 is global.
Even if used in a subcircuit, it is global
ground. You can't name the pin of a
hierarchical symbol "0" and have that
refer to the node "0" inside that page of
circuitry.

Note that you can specify other nodes to
be globals with the .global dot command.

Hello Mike,
thanks for the answer. I really felt like a beginner when I stumbled
about such a basic question.

Best Rgeards
Helmut

--- In LTspice@..., "brusque.listas@c..."
<brusque.listas@c...> wrote:

Hello,

I'm trying to have a working TRIAC model on LTSpice.

From www.teccor.com I got the following model that I saved to

a

file called triac.sub. I've put this file on lib&#92;sub folder. On the
squematic I've put the ".INCLUDE triac.sub" Spice directive.

Hello Brusque,
you were faster with your second posting as I could answer your first
one. I wanted to recommend the teccor company too.

But everytime I try to start the simulation I got the message:
SPICE Error
Too many parameters for subcircuit type "q8025r5"(instance:

xu1)

On the "Component Attribute Editor" I have:
Prefix X
InstName U1
SpiceModel triac
Value Q8025R5
Value2 <none>
SpiceLine <none>
SliceLine2 <none>

Please, I need help.

The field SpiceModel must be empty. That's the only mistake.

You only add the TRIAC symbol from the "misc" directory. Then "right
click" the mouse over the word TRIAC and change it to Q8025R5.
Shure, the command line with the models must be added to the
schematic. Example: .INCLUDE tectriac.lib . Put this file into the
lib&#92;sub directory of SwitcherCADIII.

Have you read the datasheet of this high power TRIAC? It needs nearly
100mA gate current to switch on. Just a hint for the circuit in your
simulation.

Have fun with LTSPICE.

Helmut

Brusque
--
-----------------------------------------------------------------
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Research and Development Blumenau - SC - Brazil
Say NO to HTML mail www.citronics.com.br
-----------------------------------------------------------------

Arnold Esper wrote:

An: "'LTspice@...'" <LTspice@...>

Von: "Schaich, Peter" <schaich.peter@...>
Datum: Wed, 26 Mar 2003 08:01:58 +0100
Betreff:[LTspice] Suggestions for waveform viewer



> Hi there,
>
>
> LTSpice is really fun to work with. Assuming that Mike likes to get
> feedback, I would like to make some suggestions for enhancements of the
> waveform viewer, mainly for documentation purposes:
>
> * If any parameter of the circuit is stepped with the .step command, it
> should be possible in the waveform viewer to see what value the parameter
> has in the respective curve. (see example stempodelparam.asc) Preferably
> on a legend that can be switched on or off.
>
> * the number of the cursor should always be displayed, not only on
> mouseover.
>
> * maybe it should be possible to add some draw elements for documentation
>
> * add a second color profile for the use of the results (via clipboard
> copy) in other documents with white background and different colors for
> grid, cursors and axis (cursor color is currently not customizable). There
> is no doubt that black background is good for working on the screen but
> white background is good for documentation.
>
> What are your thoughts?
>
> Regards
>
> Peter Schaich

Yes, it's a good Idea to allow white background to the graphik Window, in order
to save printing-color or some extra work for inverting it for other programs.
The black background reminds me my analog oszilloscope, earlier used every day.
But nowadays I'm almost afraid to touch it's knobs, because of the huge dust on
it.
Maybe a good Idea too, to allow some differnt styles of drawing lines like
dotted, hatched .... for black and white coying machines. Adding the unit behind
every number can make it difficult to read at high line-densities. The Windows
could have a look similar to the picture below, I made with an early Version of
Spice2.
.
Thanks, Arnold


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Mike and group:
I'll throw one out. I would like a saved setup file so that when
multiple plot planes are used I don't have to reset them up once I have
closed the file. I think a work around right now is open the schematic
file and the last raw file then rerun with changes, but I haven't tried
it yet. Mike I can't repeat myself enough about how useful the program
is.
Comments welcome
Jim Stockton

Hello,

I'm trying to have a working TRIAC model on LTSpice.

From www.teccor.com I got the following model that I saved to a file called triac.sub. I've put this file on lib&#92;sub folder. On the squematic I've put the ".INCLUDE triac.sub" Spice directive.


*=========================*
* TECCOR TRIACS *
* Triac pinout: MT2 G MT1 *
*=========================*

*SRC=Q8025R5;Q8025R5;TRIACS;TECCOR;800V 25A
*SYM=TRIAC
.SUBCKT Q8025R5 1 2 3
* TERMINALS: MT2 G MT1
QN1 5 4 3 NOUT OFF
QN2 11 6 7 NOUT OFF
QP1 6 11 3 POUT OFF
QP2 4 5 7 POUT OFF
DF 4 5 DZ OFF
DR 6 11 DZ OFF
RF 4 6 8MEG
RT2 1 7 25.4M
RH 7 6 5.25
RGP 8 3 12
RG 2 8 5.8
RS 8 4 1.2
DN 9 2 DIN OFF
RN 9 3 6.12
GNN 6 7 9 3 0.554
GNP 4 5 9 3 0.705
DP 2 10 DIP OFF
RP 10 3 3.56
GP 7 6 10 3 0.373
.MODEL DIN D (IS=764F)
.MODEL DIP D (IS=764F N=1.19)
.MODEL DZ D (IS=764F N=1.5 IBV=100U BV=800)
.MODEL POUT PNP (IS=764F BF=5 CJE=1.12N TF=102U)
.MODEL NOUT NPN (IS=764F BF=20 CJE=1.12N CJC=223P TF=6.8U)
.ENDS



But everytime I try to start the simulation I got the message:
SPICE Error
Too many parameters for subcircuit type "q8025r5"(instance: xu1)

On the "Component Attribute Editor" I have:
Prefix X
InstName U1
SpiceModel triac
Value Q8025R5
Value2 <none>
SpiceLine <none>
SliceLine2 <none>

Please, I need help.

Thanks,

Brusque
--
-----------------------------------------------------------------
Edson Brusque C.I.Tronics Lighting Designers Ltda
Research and Development Blumenau - SC - Brazil
Say NO to HTML mail www.citronics.com.br
-----------------------------------------------------------------

You are correct, The simulation is extremely slow. I would better

say

LTSPICE fails here with its default settings.

Two things are necessary with this circuit.

1.
Add the option .OPTIONS abstol=1e-10 or higher.
This reduces the numerical conergence effort for the simulator.

2. Add a load resistor of 1MOhm or less(e.g. 100k) from your output
VOUT to ground.

Only both changes together allow a useful simulation of this

circuit

with LTSPICE. I needed 1 hour to fix it even as a frequently SPICE
user. I have not further investigated which of the models in your
circuit was the trouble maker. The models used are MOSFET 2N7002,
MOSFET FDN304P and the battery switch LTC4412.
I tried a lot of the other options too, but only "abstol" and the
circuit enhancement(load resistor) were really important.


Best Regards
Helmut

Thanks Helmut!!!

What do you think about the display of the .step
Parameters in the Viewer? Or did I miss something
here, too?

This is a known problem that I want to fix. It's
not the top priority because there isn't much in
house interest in it. The IC designers using the
program tell me they feel they have no trouble
keeping the step values straight in their heads.
God bless them is all I can say. Anyway, right
now the only thing that helps here at all is that
you can use the attached cursor and navigate
sequentially from run to run in the .step with
the up/down cursor keys. Also, the .step values
used are in the .log file.

--Mike

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--- In LTspice@..., "David Pariseau"
<david.pariseau@s...> wrote:

....
I added this and commented out the Diode line and there are no

errors

now in simulation, but the simulation is glacially slow and I'm not
sure correct.

Hello Dave,
thanks for the circuit file.
When I opened it, the resistor R1 wasn't connected correctly to the
4th pin of the FDN304p. I corrected that myself.

You are correct, The simulation is extremely slow. I would better say
LTSPICE fails here with its default settings.

Two things are necessary with this circuit.

1.
Add the option .OPTIONS abstol=1e-10 or higher.
This reduces the numerical conergence effort for the simulator.

2. Add a load resistor of 1MOhm or less(e.g. 100k) from your output
VOUT to ground.

Only both changes together allow a useful simulation of this circuit
with LTSPICE. I needed 1 hour to fix it even as a frequently SPICE
user. I have not further investigated which of the models in your
circuit was the trouble maker. The models used are MOSFET 2N7002,
MOSFET FDN304P and the battery switch LTC4412.
I tried a lot of the other options too, but only "abstol" and the
circuit enhancement(load resistor) were really important.


Best Regards
Helmut

Jon,

...Edit=>Attributes=>Edit Window...

However, it's really:

Edit=>Attributes=>Attribute Window

Thank you very much for pointing this out.

Also, as I discovered, there are some items
not present in the attribute window which
appears, using ctrl-W:

2 RefName
5 QArea
8 Width
9 Length
10 Multi

Are there others I've missed? Are these
documented? Is there a reason why these
do not appear in the ctrl-W list?

There are a couple hundred symbol attributes.
There's even an undocumented attribute
compiler. These attributes are used when
LTspice reads some other EDA formats used
inhouse. However, these formats are non-
standard, customized versions of commercial
syntaxs and have no usage outside of LT.
I only document what I think is useful(and
feel I can let people rely on.) While
there are useful undocumented features
that come out in formums like this user
group, I'm afraid those symbol attributes
will be a red herring for you and could
cause erratic program operation.

--Mike

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Note that the background color is not printed. That

is, you can set it to black in the color preferences

dialog but it will still be white when you print it

on white paper becuase it's the background and is not

printed. So if you also what a bitmap that is on a

white background, so a print preview and capture that

bitmap with Alt-Print Screen.

Hope this helps,

Thanks for this hint. That's absolutely sufficient.




What do you think about the display of the .step Parameters in the
Viewer? Or did I miss something here, too?




Regards




Peter

On Wed, 26 Mar 2003 11:12:51 -0800 (PST), you wrote:

...So I looked at the ASCII text of PUT.ASY and
noticed these lines:

WINDOW 0 24 0 Left 0
WINDOW 3 24 72 Left 0
...

I'd recommend using the graphical symbol editor.
Attribute visibility is covered in help in
Schematic Capture=>Creating New Symbols=>
Attribute Visibility.

Yes, I thought I'd already tried that but apparently I hadn't.
Sorry about that -- defective user, I guess.

By the way, your help file describes this as:

"You can edit the visibility of attributes using the menu
command Edit=>Attributes=>Edit Window. After you select an
attribute with this dialog you will then be able to position it
as you wish with respect to the symbol."

However, it's really:

Edit=>Attributes=>Attribute Window

There is no "Edit Window" selection there, I believe.

Also, as I discovered, there are some items not present in the
attribute window which appears, using ctrl-W:

2 RefName
5 QArea
8 Width
9 Length
10 Multi

Are there others I've missed? Are these documented? Is there a
reason why these do not appear in the ctrl-W list?

Jon