LTwiki-Wiki for LTspice - User contributions [en]

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T14:21:51Z

Rodgaard:

LTspice supports parametric sweeps trough the .step directive:

.step param RLoad list 5 10 15

which performs three simulations with the global parameter RLoad being 5, 10 and 15. The simulation will return three results, which can be plotted in relation to time or frequency, depending on the type of analysis (transient or AC analysis). But this way of displaying the results is very incomprehensible when having more than 3-5 steps, as the results visually stacks on each other. A way of getting more comprehensible results the .measure directive can be used to perform individual measurements in the circuit:

.measure I_RLload AVG I(RL)

which returns the average current trough the resistor RL. The results of the defined measurements are printed in the "SPICE Error Log" and can be extracted from this log file.

View -> SPICE Error Log

But LTspice actually also supports Parametric plots, which is achieved by right clicking on the open "SPICE Error Log" and selecting "Plot .step'ed .meas data":

SPICE Error Log -> Right click -> Plot .step'ed .meas data

Now the measurements are plotted in relation to the swept parameter, giving a much more compressed and clear visualization of the results, enabling the user to understand the circuit dependencies of the swept parameter. Furthermore the measurements can now be exported from the Parametric plot, to a more useful format than the "SPICE Error Log":

File -> Export

[[File:LTspice parametric plot.png|1200px|thumb|left|Example of a parametric sweep and parametric plot]]

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T14:20:03Z

Rodgaard:

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T14:19:13Z

Rodgaard:

LTspice supports parametric sweeps trough the .step directive:

.step param RLoad list 5 10 15

which performs three simulations with the global parameter RLoad being 5, 10 and 15. The simulation will return three results, which can be plotted in relation to time or frequency, depending on the type of analysis (transient or AC analysis). But this way of displaying the results is very incomprehensible when having more than 3-5 steps, as the results visually stacks on each other. A way of getting more comprehensible results the .measure directive can be used to perform individual measurements in the circuit:

.measure I_RLload AVG I(RL)

which returns the average current trough the resistor RL. The results of the defined measurements are printed in the "SPICE Error Log" and can be extracted from this log file.

View -> SPICE Error Log

But LTspice actually also supports Parametric plots, which is achieved by right clicking on the open "SPICE Error Log" and selecting "Plot .step'ed .meas data":

SPICE Error Log -> Right click -> Plot .step'ed .meas data

Now the measurements are plotted in relation to the swept parameter, giving a much more compressed and clear visualization of the results, enabling the user to understand the circuit dependencies of the swept parameter. Furthermore the measurements can be exported, from the Parametric plot, to a more useful format than the "SPICE Error Log":

File -> Export

[[File:LTspice parametric plot.png|1200px|thumb|left]]

File:LTspice parametric plot.png

2013-03-07T14:13:39Z

Rodgaard:

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T14:11:39Z

Rodgaard:

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T14:10:35Z

Rodgaard:

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T13:59:44Z

Rodgaard:

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T13:32:24Z

Rodgaard:

LTspice supports parametric sweeps trough the .step directive

.step param RLoad list 5 10 15

which performs three simulations with the global parameter RLoad being 5, 10 and 15. The simulation will return three results, which can be plotted in relation to time or frequency, depending on the type of analysis (transient or AC analysis). But this way of displaying the results are very in-comprehensive when having more than 3-4 steps. A way of getting more comprehensible results the .measure directive can be used, to perform individual measurements in the circuit

.measure I_RLload AVG I(RL)

which returns the average current trough the resistor RL. The results of the defined measurements are printed in the SPICE error log

View -> SPICE Error Log

Parametric plot (plot measurements in relation to a swept parameter)

2013-03-07T12:31:32Z

Rodgaard: Created page with "LTspice supports parametric sweeps trough the .step directive .step param RLoad LIST 5 10 15 which performs three simulation with global parameter RLoad being 5, 10 and 15."

LTspice supports parametric sweeps trough the .step directive

.step param RLoad LIST 5 10 15

which performs three simulation with global parameter RLoad being 5, 10 and 15.

Tutorials relevant to Design and Modelling

2013-03-07T12:18:01Z

Rodgaard:

[http://www.eetimes.com//design/power-management-design/4218373/Calculating-power-loss-in-switching-MOSFETs?cid=NL_EETimesDaily Calculating Power Loss in switching MOSFETs] 
[[EMI Modelling using LTspice Hints]] 
[[Pure Inductor and Voltage Source Modelling (and how to speed up simulations with them) using LTspice]] 
[http://www.eetimes.com//design/power-management-design/4012153/IGBT-tutorial--Part-1--Selection?cid=NL_EETimesDaily IGBT Tutorial] 
[[O-device (Lossy Transmission Line) and T-device (Lossless Transmission Line) modelling issues]] 
[http://ltwiki.org/images/9/9e/Erno_Borbely_fet_articel_1.pdf Erno Borbely JFET Article No. 1 Operation and Practical Considerations] 
[http://info.ee.surrey.ac.uk/Workshop/advice/coils/gap/index.html Air Gapped Magnetic Cores - Analysis and why you may want them] 
[http://ltwiki.org/images/b/b1/Erno_Borbely_fet_articel_2.pdf Erno Borbely JFET Article No. 2 Operation and Practical Considerations] 
[[File:PWM_Filters.pdf]] Jim Wagner's white paper on PWM filtering 
[http://tonnesoftware.com/appnotes/pwm/pwmham.html The Pulse-Width Modulator with an emphasis on the post-modulator lowpass filter] 
[http://www.omicron-lab.com/fileadmin/assets/customer_examples/Bode_Info_LoopGain_V1_0.pdf Loop Gain by Voltage Injection] 
[http://www.littelfuse.com/data/en/Product_Catalogs/PowerThyristorApplicationNotes.pdf Fundamental Characteristics of Thyristors] 
[http://www.vlsi.uwaterloo.ca/~manis/ece637/lecture11.pdf Pass Transistor Logic] 
[[LTspice has a built in Triangle Wave]] 
[[Parametric plot (plot measurements in relation to a swept parameter)]]