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Linear Technology Corporation logo.svg
Developer(s) Linear Technology
Stable release
XVII / November 18, 2016; 22 months ago (2016-11-18)[1]
Operating system Windows, OS X
Available in English
Type Electronic design automation
License Freeware[2][3]

LTspice is freeware[2][3] computer software implementing a SPICE simulator of electronic circuits, produced by semiconductor manufacturer Linear Technology (LTC), now part of Analog Devices.[4][5]


LTspice IV provides a schematic capture and waveform viewer with enhancements and models to speed the simulation of switching regulators. Supplied with LTspice IV are macro models for 80% of LTC's switching regulators and operational amplifiers, transistors, MOSFETs, and passive components.

LTspice IV is node-unlimited and third-party models can be imported. Circuit simulations based on transient, AC, noise and DC analysis can be plotted as well as Fourier analysis. Heat dissipation of components can be calculated and efficiency reports can also be generated.

LTspice IV is used within LTC, and by many users in fields including radio frequency electronics, power electronics, digital electronics, and other disciplines. LTspice IV does not generate printed circuit board (PCB) layouts, but netlists can be imported into layout programs. While LTspice does support simple logic gate simulation, it is not designed specifically for simulating logic circuits.

LTspice was originally called SwitcherCAD and is sometimes still called by that name. The software is maintained by Mike Engelhardt. The application is written for Microsoft Windows but, since 2003,[6] it will run under the Wine Windows compatibility layer under Linux. Since 2013 there is also a native OS X version available, albeit with a crippled user interface that lacks essential features such as the command toolbar. From version IV LTspice requires at least a Pentium 4 processor and Windows 2000 or later.[7]

In 2016 LTspice XVII was released. It runs on 32- or 64-bit editions of Windows 7, 8, and 10.[8]

File format[edit]

Many of the LTspice files are stored as an ASCII text file, which can be viewed or edited with any ASCII text editor programs. One of the side benefits of an ASCII file format is that a schematic can be listed in a printed document or book, which allows the reader to recreate LTspice files without electronic file distribution.

LTspice filename extensions:[9]

  • asc - schematic.[9]
  • asy - symbol shown in a schematic.[9]
  • cir - external netlist input file.[9]
  • lib - model library subcircuits.[10]
  • plt - waveform viewer plot settings.[9]
  • sub - subcircuit.[10]

Schematic files[edit]

LTspice schematics are stored as an ASCII text file with a filename extension of "asc".[9] It consists of a netlist based on SPICE text-based commands.

The following example shows the contents from a small LTspice schematic file for a simple RC circuit with 4 symbols: 10 volt DC voltage source, 1K ohm resistor, 10 uF capacitor, ground symbol. The bottom two lines are a transient simulation directive with a stop time parameter of 10 ms (.tran 0.01), and a SPICE directive to set the initial RC "output" condition to zero volts (.ic v(output)=0). This schematic can be viewed by copying the text, pasting it into an ASCII text editor, saving it as file with the file extension of "asc", then opening the file with LTspice.

Version 4
SHEET 1 880 680
WIRE 224 96 128 96
WIRE 128 160 128 96
WIRE 224 192 224 176
WIRE 288 192 224 192
WIRE 224 208 224 192
WIRE 128 288 128 240
WIRE 224 288 224 272
WIRE 224 288 128 288
WIRE 224 304 224 288
FLAG 224 304 0
FLAG 288 192 output
SYMBOL res 208 80 R0
SYMBOL cap 208 208 R0
SYMATTR SpiceLine V=50
SYMBOL voltage 128 144 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
TEXT 118 344 Left 2 !.tran 0.01
TEXT 120 376 Left 2 !.ic v(output)=0

See also[edit]


  1. ^
  2. ^ a b Mike Engelhardt: LTspice IV Help → F.A.Q. → License and Distribution. (Help of software version 4.19u of 4 September 2013)
  3. ^ a b Mike Engelhardt: LTspice IV Help → Introduction → License Agreement/Disclaimer. (Help of software version 4.19u of 4 September 2013)
  4. ^ LTspice IV Circuit Simulation Schematic Capture Tool
  5. ^ Pell, Rich (January 13, 2009). "Free SPICE software exploits multicore processors". EE Times. Retrieved January 17, 2011.
  6. ^ news:sci.electronics.cad: LTspice/SwitcherCAD III now runs on Linux accessdate=September 27, 2013
  7. ^ news:sci.electronics.cad: Announce: Multi-threaded LTspice accessdate=September 27, 2013
  8. ^
  9. ^ a b c d e f What are the different LTspice file types; LTwiki.
  10. ^ a b Subcircuit structure guide; Audio perfection.

External links[edit]

Linear Technology