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If I have several parameters which I am stepping in a simulation, does it go through all combinations?

For example, if I step a resistor, Rxx, in 3 steps ... and also step a capacitor Cyy, in 3 steps, will it go through all 9 value combinations or will it do 3 simulations, with the stepped R and C values?

Thanks for your patience,

Rob

I need a modell for LM4041-ADJ (National). Please help me.

--- In LTspice@..., "marius_darie" <marius_darie@...> wrote:

How can I implement a (time dependent or automate)
continuous variable load resistance for simulating
various regimes in cc circuit and power dissipation
in circuit's components.

Thank you!

Hello,

You could use "time" in an equation for the resistance.
Instead of the value 10 for example, you write an equation
as shown below.

R=10*(1-0.9*u(time-2m))

Resistance versus time in this case:
t<=2ms : R=10 Ohm
t>ms : R=1 Ohm

This resistor has effectively become a B-source. Please look
in the help pages for the possible functions with B-sources.


I normally use pulsed current sources for the test of
load transients.

Best regards,
Helmut

--- In LTspice@..., "f0xwm" <yfuji@...> wrote:

Hi,

I am trying to figure out a way to plot gm/Id for a
transistor within LTspice. I am using as a starting
point the schematic in the example MOSFET parameter
sweep, MOS_gm_gmb_gds_ro.asc , within
Examples&#92;Examples&#92;Educational&#92;MOSFET parameter sweep&#92; .

In short, I am stepping the W/L and biasing sources
and running .OP and .AC LIST 1 analysis . The example
computes gm, gmb, gds, using the small-signal values
from the AC analysis.

To plot gm/Id I would need to obtain the bias current
of the NMOS transistor, either from the DC current
through the voltage sources or through the device
itself. Is there a way to refer to this current from
the waveform viewer, maybe a trick I am missing ?
The Spice Log file lists the device operating point
for just one iteration, so I don't see how to extract
the bias information for the steps, which is obviously
being computed prior to the each AC analysis.

In short, given a sequence of AC analysis, how can I
obtain/extract the bias point information for the
circuit/devices, and if possible refer/use it within
the waveform view when plotting ?

Helmut, can you help ? Mike, are you out there ?
Fellow users, any ideas/work arounds ?

Thanks in advance for any help!

Hello,

You should use the .DC analysis in this case. Please take a
look the examples.

Files > Tut > Transconductance Gm and Gds



Best regards,
Helmut

Hi,

I am trying to figure out a way to plot gm/Id for a transistor within LTspice. I am using as a starting point the schematic in the example MOSFET parameter sweep, MOS_gm_gmb_gds_ro.asc , within Examples&#92;Examples&#92;Educational&#92;MOSFET parameter sweep&#92; .

In short, I am stepping the W/L and biasing sources and running .OP and .AC LIST 1 analysis . The example computes gm, gmb, gds, using the small-signal values from the AC analysis.

To plot gm/Id I would need to obtain the bias current of the NMOS transistor, either from the DC current through the voltage sources or through the device itself. Is there a way to refer to this current from the waveform viewer, maybe a trick I am missing ? The Spice Log file lists the device operating point for just one iteration, so I don't see how to extract the bias information for the steps, which is obviously being computed prior to the each AC analysis.

In short, given a sequence of AC analysis, how can I obtain/extract the bias point information for the circuit/devices, and if possible refer/use it within the waveform view when plotting ?

Helmut, can you help ? Mike, are you out there ? Fellow users, any ideas/work arounds ?

Thanks in advance for any help!

How can I implement a (time dependent or automate) continuous variable load resistance for simulating various regimes in cc circuit and power dissipation in circuit's components.

Thank you!

--- In LTspice@..., "Rick" <sawreyrw@...> wrote:

--- In LTspice@..., Philip Bellingham <rmhc78a@> wrote:

Emma,
?

I would also suggest changing your output load from a constant current to a resistor or some thing that more closely approximates a real world load. There are times in this simulation when both IGBTs are off. Since the current source still tries to maintain the specified current, the output voltage will have a magnitude of several thousand volts due to the current source forcing the current through the high impedance presented by the cut-off transistors.
?
I have uploaded a version of your schematic file modified as I have suggested (igbt_infineon_modified.asc). It ran for me using the Normal solver with modified trap integration.
?
Regards,
?
?? - Philip

Typically, the load on IGBTs is highly inductive so it is appropriate to use a current source as a load. Therefore, you need reverse diodes across the IGBTs.

There is obviously something wrong with the IGBT model, since the simulation takes so long.

See faq_11.txt under the Files=>FAQ section of this group for information on timestep and convergence problems.

Rick

Hi Rick and Philip,

Thanks for your comments, they were very helpful! Now I have included freewheeling diodes to the transistors, included "OFF" and I also have a small inductance (1e-6H) in series with the current source at the load. The load is suppose to represent a PMSM motor, that's why I thought I could use a current source as representation. The simulation can now run, thanks!

Kind Regards,
Emma

--- In LTspice@..., "youarecrazydude" <youarecrazydude@...> wrote:

Our class instructor requires Date and Name on LTSpice
screenshots (to prevent cheating, I think). I have not
figured out how to add Date And Name to LTSpice plots.
Is there a way of automatic generation, say, via spice
directive? (I would hate to copy and paste the sucker,
manually, to all the plots, or, worse, to use third
party-app to do it).

Hello,

You can add comments (e.g. the date) to plots in the
waveform viewer.

Plot Settings -> Notes and Annotations -> Place Text

Now you can use "Tools -> Copy Bitmap to Clipboard" to get
the picture with the added comment(date).


After this work, you should save the plot settings.

Plot Settings -> Save Plot Settings

Best regards,
Helmut

Hello Helmut,

"This file contains a PowerPoint file(.ppt) with Mike's
presentation. Please open this ppt-file in the presentation
mode. Then you can directly open the hyperlinked examples
by clciking on the arrow-icons in the slides. This feature
only works with MS-PowerPoint, but not with OpenOffice-Impress."

I haven't been able to get the feature to work with 2007 PowerPoint Viewer either.


Regards,

Howard


Howard.Rogers@...

Hello Helmut,
What are you meaning by " LTspice uses the whole
screen. " ?
As you can see in my little benchmarks, there a big difference between mini and maxi ?
And I deleted some curious results.
In fact, I think that a lot of parameters ( graphic card, Windows or Unix, ............) are to be in head.
By the way : simulations, on my PC, seem to be a little bit longer with 4.00c ?
Best regards
Philippe

just kidding

seriously, I mean it, I would pay someone to generate some transistor models for me. SERIOUSLY.

There's no point in me trying to do it myself, it would take a year and I'd never get it right anyway.

I have googled for these for hours, have searched the archives, and I'm just chasing my tail on these.

I would prefer subcircuits, but, trust me, I'd be perfectly happy with models.

Or, I would settle for models/subcircuits for devices that are analogs of these. And, I don't expect (of course) the models/subcircuits to be perfect.

If you are good at generating SS models/subcircuits, please contact me off-list. I will have more in the future. I will also post them for free; this is not for proprietary use, I just need 'em!!

The ones I ESPECIALLY need right now are (models/subcircuits/analogs):

Exicon ECF20N25A (nmos lateral mosfet)
Exicon ECF20P25EA (pmos lateral mosfet)
Fairchild KSC1845U
Sanken 2SC2911
Sanken 2SA1209
Exicon EXC10N20
Exicon EXC10P20

best, charlie

Hi Howard,

You're right. The first Models of 555/556 was from
the LTspice "Masc." folder. The second attempt
was the transistor realization from LTspice's
/examples/Educational NE555.asc, following
Mike's advise. Behavioral and transistor model gave me
the same (wrong) results for small signal inputs.
I investigated on the website and I found a few different
realization of these subcircuits, but they had the same
problems.

Correctly the problem was with low voltage behavior of
Trigger and Threshold inputs. I tried to make PWM circuitry
which was perfect in simulation in range of 0 to Vcc, but on
the bench the physical realization felt under 1V ov input voltage.
I asked for samples from IC vendors (ST, TI). On both these
imputes behaved differently, they lost linearity under
1V at Vcc=5V.

Regards,
Peter

--- In LTspice@..., "philippe b" <basier.philippe@...> wrote:

Hello "????",

I made some benchmarks on my PC.
I made an excel file.
Are you interested ?
How send it on the group ?
Regards,
Philippe

Hello Philippe,

Please upload your file to the Files section.

Files > Temp



Best regards,
Helmut


PS: By the way, I have discoverd that the simulation time of
analog's test circuit is longer if LTspice uses the whole
screen.

--- In LTspice@..., "Ken" <kpotter999@...> wrote:

--- In LTspice@..., "Helmut" <helmutsennewald@> wrote:

--- In LTspice@..., "kpotter999" <kpotter999@> wrote:

Dear Group Members,

I have been attempting to use the following commands
to calculate the output rise and fall times of an inverter
and the propagation delay with the following voltage source:

PULSE(0 3.3 1n 1.5n 1.5n 5n 10n)

.MEAS TRAN fall_delay
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1

.MEAS TRAN rise_delay
+ TRIG V(Vout) VAL=3.3*0.1 TD=0NS RISE=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0NS RISE=1

.MEAS TRAN propagation_fall
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 RISE=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 FALL=1

.MEAS TRAN propagation_rise
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 RISE=1

Unfortunately the results from the .MEAS text do not
agree with manual plotting and reading of the waveforms.

i.e.

From Waveform, Rise time = 118ps, Fall time = 152ps

From text, Rise time = 6.7ns, Fall time = 1.6ns

Clearly, I am doing something fundamentally wrong with
the .MEAS command but I have been unable to resolve
this further. I would really appreciatte some feedback
and can supply the circuit schematic and inverter model
if required.

Many thank, Ken Potter.

Hello Ken,

I have uplaoded an example for you.

Files > Tut > MEASURE > TRAN >RC_measure_rise_fall_delay.asc



I have used the following MEASURE-commands.

.MEAS t1r WHEN V(out)=0.1*5 TD=0 RISE=2
.MEAS t2r WHEN V(out)=0.9*5 TD=0 RISE=2

.MEAS t1f WHEN V(out)=0.9*5 TD=0 FALL=2
.MEAS t2f WHEN V(out)=0.1*5 TD=0 FALL=2

.MEAS tdr1 WHEN V(in)=0.5*5 TD=0 RISE=2
.MEAS tdr2 WHEN V(out)=0.5*5 RISE=2

.MEAS tdf1 WHEN V(in)=0.5*5 TD=0 FALL=2
.MEAS tdf2 WHEN V(out)=0.5*5 TD=0 FALL=2

.MEAS trise PARAM t2r-t1r
.MEAS tfall PARAM t2f-t1f
.MEASURE tdelay_rise PARAM tdr2-tdr1
.MEASURE tdelay_fall PARAM tdf2-tdf1

Best regards,
Helmut

Dear Helmut,

Thank you very much for your reply, I will go and figure this out.

Regards, Ken.

Dear Helmut,

Just to let you know that worked perfectly! Very gratefull, Ken.

Hello "????",

I made some benchmarks on my PC.
I made an excel file.
Are you interested ?
How send it on the group ?
Regards,
Philippe

--- In LTspice@..., "heifetz.7777" <heifetz.7777@> wrote:

2. You have another file LM317.lib in the path
"C:&#92;Program Files&#92;LTC&#92;LTspiceIV&#92;lib&#92;sub&#92;".
This is the path where LTspice firstly look for included
files.

Best regards,
Helmut

Thank you very much! That was the problem. Runs just fine now.

A tip of the hat!
Paul

Our class instructor requires Date and Name on LTSpice screenshots (to prevent cheating, I think). I have not figured out how to add Date And Name to LTSpice plots. Is there a way of automatic generation, say, via spice directive? (I would hate to copy and paste the sucker, manually, to all the plots, or, worse, to use third party-app to do it).

--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:

--- In LTspice@..., "kpotter999" <kpotter999@> wrote:

Dear Group Members,

I have been attempting to use the following commands
to calculate the output rise and fall times of an inverter
and the propagation delay with the following voltage source:

PULSE(0 3.3 1n 1.5n 1.5n 5n 10n)

.MEAS TRAN fall_delay
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1

.MEAS TRAN rise_delay
+ TRIG V(Vout) VAL=3.3*0.1 TD=0NS RISE=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0NS RISE=1

.MEAS TRAN propagation_fall
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 RISE=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 FALL=1

.MEAS TRAN propagation_rise
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 RISE=1

Unfortunately the results from the .MEAS text do not
agree with manual plotting and reading of the waveforms.

i.e.

From Waveform, Rise time = 118ps, Fall time = 152ps

From text, Rise time = 6.7ns, Fall time = 1.6ns

Clearly, I am doing something fundamentally wrong with
the .MEAS command but I have been unable to resolve
this further. I would really appreciatte some feedback
and can supply the circuit schematic and inverter model
if required.

Many thank, Ken Potter.

Hello Ken,

I have uplaoded an example for you.

Files > Tut > MEASURE > TRAN >RC_measure_rise_fall_delay.asc



I have used the following MEASURE-commands.

.MEAS t1r WHEN V(out)=0.1*5 TD=0 RISE=2
.MEAS t2r WHEN V(out)=0.9*5 TD=0 RISE=2

.MEAS t1f WHEN V(out)=0.9*5 TD=0 FALL=2
.MEAS t2f WHEN V(out)=0.1*5 TD=0 FALL=2

.MEAS tdr1 WHEN V(in)=0.5*5 TD=0 RISE=2
.MEAS tdr2 WHEN V(out)=0.5*5 RISE=2

.MEAS tdf1 WHEN V(in)=0.5*5 TD=0 FALL=2
.MEAS tdf2 WHEN V(out)=0.5*5 TD=0 FALL=2

.MEAS trise PARAM t2r-t1r
.MEAS tfall PARAM t2f-t1f
.MEASURE tdelay_rise PARAM tdr2-tdr1
.MEASURE tdelay_fall PARAM tdf2-tdf1

Best regards,
Helmut

Dear Helmut,

Thank you very much for your reply, I will go and figure this out.

Regards, Ken.

--- In LTspice@..., "kpotter999" <kpotter999@...> wrote:

Dear Group Members,

I have been attempting to use the following commands
to calculate the output rise and fall times of an inverter
and the propagation delay with the following voltage source:

PULSE(0 3.3 1n 1.5n 1.5n 5n 10n)

.MEAS TRAN fall_delay
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1

.MEAS TRAN rise_delay
+ TRIG V(Vout) VAL=3.3*0.1 TD=0NS RISE=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0NS RISE=1

.MEAS TRAN propagation_fall
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 RISE=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 FALL=1

.MEAS TRAN propagation_rise
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 RISE=1

Unfortunately the results from the .MEAS text do not
agree with manual plotting and reading of the waveforms.

i.e.

From Waveform, Rise time = 118ps, Fall time = 152ps

From text, Rise time = 6.7ns, Fall time = 1.6ns

Clearly, I am doing something fundamentally wrong with
the .MEAS command but I have been unable to resolve
this further. I would really appreciatte some feedback
and can supply the circuit schematic and inverter model
if required.

Many thank, Ken Potter.

Hello Ken,

I have uplaoded an example for you.

Files > Tut > MEASURE > TRAN >RC_measure_rise_fall_delay.asc



I have used the following MEASURE-commands.

.MEAS t1r WHEN V(out)=0.1*5 TD=0 RISE=2
.MEAS t2r WHEN V(out)=0.9*5 TD=0 RISE=2

.MEAS t1f WHEN V(out)=0.9*5 TD=0 FALL=2
.MEAS t2f WHEN V(out)=0.1*5 TD=0 FALL=2

.MEAS tdr1 WHEN V(in)=0.5*5 TD=0 RISE=2
.MEAS tdr2 WHEN V(out)=0.5*5 RISE=2

.MEAS tdf1 WHEN V(in)=0.5*5 TD=0 FALL=2
.MEAS tdf2 WHEN V(out)=0.5*5 TD=0 FALL=2

.MEAS trise PARAM t2r-t1r
.MEAS tfall PARAM t2f-t1f
.MEASURE tdelay_rise PARAM tdr2-tdr1
.MEASURE tdelay_fall PARAM tdf2-tdf1

Best regards,
Helmut

--- In LTspice@..., "kpotter999" <kpotter999@...> wrote:

Dear Group Members,

I have been attempting to use the following commands to calculate the output rise and fall times of an inverter and the propagation delay with the following voltage source:

PULSE(0 3.3 1n 1.5n 1.5n 5n 10n)

.MEAS TRAN fall_delay
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1

.MEAS TRAN rise_delay
+ TRIG V(Vout) VAL=3.3*0.1 TD=0NS RISE=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0NS RISE=1

.MEAS TRAN propagation_fall
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 RISE=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 FALL=1

.MEAS TRAN propagation_rise
+ TRIG V(Vin) VAL=3.3*0.5 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.5 TD=0 RISE=1

Unfortunately the results from the .MEAS text do not agree with manual plotting and reading of the waveforms.

i.e.

From Waveform, Rise time = 118ps, Fall time = 152ps

From text, Rise time = 6.7ns, Fall time = 1.6ns

Clearly, I am doing something fundamentally wrong with the .MEAS command but I have been unable to resolve this further. I would really appreciatte some feedback and can supply the circuit schematic and inverter model if required.

Many thank, Ken Potter.

PLEASE IGNORE THE TYPING ERROR the 3rd line should say 3.3*0.1

.MEAS TRAN fall_delay

+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1
+ TRIG V(Vout) VAL=3.3*0.9 TD=0 FALL=1