Analysis

LTspice-Simulation Commands Setting

In this article, we will explain in detail how to set the simulation command used for the following six types of analysis.

Edit Simulation Command
  • Transient Analysis(.tran)
  • AC Analysis(.ac)
  • DC Sweep Analysis(.dc)
  • Noise Analysis(.noise)
  • DC Transfer Function Analysis(.tf)
  • DC Operating Point Analysis(.op)

The simulation commands used for these six types of analysis can be easily set with “Edit Simulation Command”.

For the types of analysis, please see the following article.

How to open “Edit Simulation Command”

Simulation command settings can be made on the “Edit Simulation Command” screen.

Click “Simulate”-“Edit Simulation Cmd” from the menu bar of the schematic editor screen to display the “Edit Simulation Command” screen.

Transient

Setting Explanation
Stop time Analysis end time
Time to start saving data Time to start saving data
Maximum Timestep Maximum value of time interval
Start external DC supply voltages at 0V Set initial value of external DC power supply to 0 V at simulation start
Stop simulating if steady state is detected Stop the simulation if steady state is detected and there is no change
Don’t reset T=0 when steady state is detected Not set
Step the load current source Step change current source
Skip initial operating point solution Set the initial value of the element to the initial value of simulation execution

AC Analysis

Setting Explanation
Type of sweep Select the type of sweep below.
Octave: Every 2 times
Decade: Every 10 times
Linear: Equal interval
List: Specified frequency in list
Number of points Number of points in simulation
Octave: Number of points per Octave (Estimate: 20 to 40)
Decade: Number of points per Decade (Estimate: 30 to 100)
Linear: Total number of points
Start frequency Analysis start frequency
Stop frequency Analysis end frequency
1st frequency/
2nd frequency/
3rd frequency
First frequency /
Second frequency /
Third frequency
* Set when “List” is selected in “Type of sweep”

DC sweep

Setting Explanation
Name of 1st source to sweep/
Name of 2nd source to sweep/
Name of 3rd source to sweep
Specify voltage source and current source to sweep
※ You can specify up to three by selecting a tab
Type of sweep Select the type of sweep below.
Octave: Every 2 times
Decade: Every 10 times
Linear: Equal interval
List: Specified frequency in list
Start value Values of voltage source and current source at the start of analysis
Stop value Values of voltage source and current source at the end of analysis
Increment Increase value
* Set when “Linear” is selected in “Type of sweep”
Number of points per Octave Number of points per Octave
※ Set when “Octave” is selected in “Type of sweep”
Number of points per Decade Number of points per decade
※ Set when “Decade” is selected in “Type of sweep”
1st value/
2nd value/
3rd value
irst voltage source or current source value /
Second voltage source or current source value /
Third voltage or current source value
* Set when “List” is selected in “Type of sweep”

Noise

Setting Explanation
Output Output signal
Input Input signal
Type of sweep Select the type of sweep below.
Octave: Every 2 times
Decade: Every 10 times
Linear: Equal interval
List: Specified frequency in list
Number of points per octave Number of points per Octave
※ Set when “Octave” is selected in “Type of sweep”
Number of points per decade Number of points per decade
※ Set when “Decade” is selected in “Type of sweep”
Number of points Total number of points
* Set when “Linear” is selected in “Type of sweep”
Start Frequency Analysis start frequency
Stop Frequency Analysis end frequency
1st frequency/
2nd frequency/
3rd frequency
First frequency /
Second frequency /
Third frequency
* Set when “List” is selected in “Type of sweep”

DC Transfer

Setting Explanation
Output Output node name
Source Input node name

DC op pnt

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