Running SPICE

DOWNLOADING THE CIRCUIT FILE

1. From the Circuit Collection page on this site, click on a circuit topic such as RC Low-Pass Filter. You’ll see a schematic along with circuit and simulation notes.

2. Download the SPICE file LPFILTER1.CIR by clicking on download the SPICE file and save to desired folder. If your browser automatically opens the text file, Right-Click and selelect Save As (be sure to remove .txt if browser appends one, leaving only the .cir.)

LTSPICE SIMULATION – STEP BY STEP

LTSPICE from Linear Technology is a powerful free version with no component limit. You can download a free demo version (See Demos and Downloads). Here’s how to run a simulation for the SPICE file named LPFILTER1.CIR, plot various results and modify the circuit.

RUNNING A SIMULATION.

1. Start the LTSPICE program.

2. To open a SPICE circuit file select Open > File. Drop down the Files of Type box and select Files of Type (*.cir) to make the *.cir files visible. Move to folder where you saved your SPICE circuit (LPFILTER.CIR), click on the filename, then click on Open. Your SPICE circuit file will appear in a text editor window.

NOTE Specify an .AC (frequency) or .TRAN (time) Analysis in the netlist but NOT both simulatenously.
Insert "*" before .AC or .TRAN to tell SPICE to ignore the line.

3. Select Simulate > Run or click the simulation icon (running man) on the top toolbar.

PLOTTING VOLTAGES AND CURRENTS.

1. LTSPICE automatically opens a PLOT window. The PRINT statement tells SPICE which waveforms to make available. Exclude it to make all voltages and currents available.

2. To add waveforms select Plot Settings > Add Traces. Click on one or more of the voltages
v(node) or currents i(device) available and then click OK.

MODIFYING YOUR CIRCUIT.

1. In the text editor’s window, modify component values or change analysis commands in your SPICE circuit file.

2. Save the file by selecting File > Save or can click the simulation icon (running man) to save and run a new simulation.

Top ↑